Case-sensitive lookup (#6) and ST2 compatibility

If no case-insensitive OS (Windows, OSX) is detected, try several common spellings to find readme files.

If `sublime.find_resources` is not defined (as in Sublime 2), use a fallback that mimicks the original behavior to the extent needed: look for files matching a pattern inside subdirectories of `sublime.packages_path()`. Unlike the original function, lookup is NOT recursive and does NOT include `sublime.installed_packages_path()`.

Tested on Linux Mint 16 with Sublime 2.0.2 and Sublime 3 (stable build 3059).

I noticed the script contains DOS/Windows line endings (CRLF), so I used them as well. You might want to check out this Github [article about line endings](https://help.github.com/articles/dealing-with-line-endings/#platform-all) to avoid confusion with people on other platforms.