Add support for rich text clipboard copy on win32

HTML still needs work, but RTF now goes onto the clipboard in its native
format!
Add win32 HTML Clipboard support

Added win32 HTML Clipboard support.
RTF clipboard copying now crashes 500% less often!
Rearranged a bit of the winclip code for reusability.
Improved win32 clipboard unicode support

win32 now copies unicode characters a bit better.  pygments escapes a
lot of these characters, so it's not a huge deal, but a few edge cases
were causing the script to fail.
Cleaned up code

Cleaned up code based on @n1k0's suggestions.
Merge pull request #19 from schmod/master

Improve win32 clipboard support