Fix errorformat for RuboCop checker

The errorformat for the RuboCop checker was missing the capture group
for the column number of the error/warning, which resulted in the
location list attempting to jump to 'filename.rb:80', which would
attempt to open a new file.

The solution was to add the "%c" to capture the column number of the
error.
Change --emacs flag to --format emacs for RuboCop

The `--emacs` flag has been deprecated. Switch to specifying
`--format emacs` so that this doesn't break when RuboCop 1.0 is
released.
Merge remote-tracking branch 'sds/fix-rubocop-errorformat'
Version check for rubocop.

Only rubocop versions 0.9.0 or later are supported.