Remove 2 spaces from Markdown lists

This improves rendering of the README.md since 4 spaces intends get treated as code.

README.md

@@ -10,11 +10,11 @@ interface to Lua right now is [hlua](https://github.com/tomaka/hlua/) which you
 should definitely check out and use if it suits your needs.  This crate has the
 following differences with hlua:
 
-    * Handles to Lua values use the Lua registry, not the stack
+  * Handles to Lua values use the Lua registry, not the stack
-    * Handles to Lua values are all internally mutable
+  * Handles to Lua values are all internally mutable
-    * Handles to Lua values use non-mutable borrows the main Lua object, so
+  * Handles to Lua values use non-mutable borrows the main Lua object, so
-      there can be multiple handles or long lived handles
+    there can be multiple handles or long lived handles
-    * Targets lua 5.3
+  * Targets lua 5.3
 
 The key difference here is that rlua handles rust-side references to Lua values
 in a fundamentally different way than hlua, more similar to other lua bindings
@@ -33,34 +33,34 @@ heavily inspired by the lua API that I previously wrote for Starbound, and will
 become feature complete with that API over time.  Some capabilities that API has
 that are on the roadmap:
 
-    * Proper coroutine support
+  * Proper coroutine support
-    * Lua profiling support
+  * Lua profiling support
-    * Execution limits like total instruction limits or lua <-> rust recursion
+  * Execution limits like total instruction limits or lua <-> rust recursion
-      limits
+    limits
-    * Security limits on the lua stdlib, and general control over the loaded
+  * Security limits on the lua stdlib, and general control over the loaded
-      lua libraries.
+    lua libraries.
-    * "Context" or "Sandboxing" support, this was probably a bit too heavyweight
+  * "Context" or "Sandboxing" support, this was probably a bit too heavyweight
-      in Starbound's API, but there will be the ability to set the _ENV upvalue
+    in Starbound's API, but there will be the ability to set the `_ENV` upvalue
-      of a loaded chunk to a table other than _G, so that you can have different
+    of a loaded chunk to a table other than `_G`, so that you can have different
-      environments for different loaded chunks.
+    environments for different loaded chunks.
 
 There are also some more general things that need to be done:
 
-    * More fleshed out Lua API, things like custom metatables and exposing the
+  * More fleshed out Lua API, things like custom metatables and exposing the
-      registry.
+    registry.
-    * MUCH better API documentation, the current API documentation is almost
+  * MUCH better API documentation, the current API documentation is almost
-      non-existent.
+    non-existent.
-    * Performance testing.
+  * Performance testing.
 
 Additionally, there are ways I would like to change this API, once support lands
 in rustc.  For example:
 
-    * Once ATCs land, there should be a way to wrap callbacks based on argument
+  * Once ATCs land, there should be a way to wrap callbacks based on argument
-      and return signature, rather than calling lua.pack / lua.unpack inside the
+    and return signature, rather than calling lua.pack / lua.unpack inside the
-      callback.  Until then, it is impossible to name the type of the function
+    callback.  Until then, it is impossible to name the type of the function
-      that would do the wrapping.
+    that would do the wrapping.
-    * Once tuple based variadic generics land, the plan is to completely
+  * Once tuple based variadic generics land, the plan is to completely
-      eliminate the lua multi macros in favor of simple tuples.
+    eliminate the lua multi macros in favor of simple tuples.
  
 See [this reddit discussion](http://www.reddit.com/r/rust/comments/5yujt6/) for
 details of the current lifetime problem with callback wrapping.
@@ -73,13 +73,13 @@ a lot of unsafe code in this crate, and I would call the current safety level
 of the crate "Work In Progress".  The GOAL is for the crate to handle tricky
 situations such as:
 
-    * Panic safety, and carrying the panic across the lua api correctly
+  * Panic safety, and carrying the panic across the lua api correctly
-    * Lua stack size checking, and correctly handling lua being out of stack
+  * Lua stack size checking, and correctly handling lua being out of stack
-      space
+    space
-    * Leaving the correct elements on the lua stack and in the correct order,
+  * Leaving the correct elements on the lua stack and in the correct order,
-      and panicking if these invariants are not met (due to internal bugs).
+    and panicking if these invariants are not met (due to internal bugs).
-    * Correctly guarding the metatables of userdata so that scripts cannot, for
+  * Correctly guarding the metatables of userdata so that scripts cannot, for
-      example, swap the __gc methods around and cause UB.
+    example, swap the `__gc` methods around and cause UB.
 
 The library currently attempts to handle each of these situations, but there
 are so many ways to cause unsafety with Lua that it just needs more testing.