Remove useless calls to executable()
Fix quoting in darcs detection
New option: signify_update_on_focusgained
Allow highlight groups overriding

The [default] argument is used for setting the default highlighting for a group. If highlighting has already been specified for the group the command will be ignored. Also when there is an existing link.
Merge pull request #52 from esneider/patch-1

Allow highlight groups overriding
Set encoding for plugin files

Closes #54.
Remove redundant path modification for diff on win32
Merge pull request 55 from bling

Closes #55.