Use auto groups, clear before write

Using autogroups to namespace the vimerl commands.
Instead of calling s:ClearErrors after the write, call it before the write.
This fixes compatibility with other plugins that add signs to the gutter.
Merge pull request #42 from armon/master

Fixing compatibility with gitgutter
Cosmetic
Temporary fix: comment compilation directive for R16 release

With the compiler shipped in R16 release the indenter script is
painfully slow to be compiled. Using as temporary fix interpreted mode.