Handle special characters in path<->uri conversion.

pkg/path/README.md

 A comprehensive, cross-platform path manipulation library for Dart.
 
 The path package provides common operations for manipulating file paths:
 joining, splitting, normalizing, etc.
 
 We've tried very hard to make this library do the "right" thing on whatever
 platform you run it on. When you use the top-level functions, it will assume the
 current platform's path style and work with that. If you want to specifically
 work with paths of a specific style, you can construct a `path.Builder` for that
 style.
 
 ## Using
 
 The path library was designed to be imported with a prefix, though you don't
 have to if you don't want to:
 
-    import 'package:path/path.dart' as path; // TODO(bob): ???
+    import 'package:path/path.dart' as path;
 
 ## Top-level functions
 
 The most common way to use the library is through the top-level functions.
 These manipulate path strings based on your current working directory and the
 path style (POSIX, Windows, or URLs) of the host platform.
 
 ### String get current
 
 Gets the path to the current working directory. In the browser, this means the
@@ skipping 369 matching lines @@
  *  It can accurately tell if a path is absolute based on drive-letters or UNC
     prefix.
 
  *  It understands that "/foo" is not an absolute path on Windows.
 
  *  It knows that "C:\foo\one.txt" and "c:/foo\two.txt" are two files in the
     same directory.
 
 If you find a problem, surprise or something that's unclear, please don't
 hesitate to [file a bug](http://dartbug.com/new) and let us know.