Improve docs and code coments

Author: josevalim

lib/elixir/lib/io.ex

@@ -152,8 +152,10 @@ defmodule IO do
 
   The `device` is iterated as specified by the `line_or_chars` argument:
 
-    * if `line_or_chars` is an integer, it represents a number of characters. The device
-      is iterated by that number of characters.
+    * if `line_or_chars` is an integer, it represents the number of characters
+      according to the device encoding (either latin1 or utf8). The device is
+      iterated by that number of characters. Use `binread/2` if you desire to
+      read bytes.
 
     * if `line_or_chars` is `:line`, the device is iterated line by line.
       CRLF newlines  ("\r\n") are automatically normalized to "\n".

lib/mix/lib/mix/project_stack.ex

@@ -10,7 +10,7 @@ defmodule Mix.ProjectStack do
   @timeout :infinity
 
   # compile.lock is not the best name, but the name is completely
-  # opaque and we keep it for backwards compatibility (just in case).
+  # opaque and we keep it for backwards compatibility.
   @manifest "compile.lock"
 
   @typep file :: binary