Merge pull request #55 from crazymaster/master

Update doc
- Improved check source.
- Improved check_source().
Detecting vim 7.4 beta
Merge pull request #58 from mv/detect-vim-7.4

Detecting vim 7.4 beta
- Fixed #60 file/include.
- Fixed #447.
- Updated vital.
- Updated vital.
- Fixed complete options.
- Fixed for preview window behavior.
- Fixed unite#print_error().
- Updated FAQ.
Fix doc