Updates to syntax completion and fixed $VIMHOME not setting properly

Syntax completion now works a little differently. When tab is used, it
will now automatically try to insert the best match. Also, the
completion menu is always visible.

Also changed the autocommand and moved file specific updates to their
own vim files in after/ftplugin.

Python omni completion now works exactly as expected. It smartly tries
to complet based on the class data (like eclipse).

Files with a filetype of log should no longer use the ErrorMsg
highlighting after 80 characters on a line.

Git commit now properly highlights characters after column 72 as error
as git commit messages by convention should never exceed 72 chars wide.