Remove use of global variables to get Regexp captures in Subtitle#shift

Since `$1` and `$2` are not completely compatible with MacRuby,
our uses changed to the similar `result[0]` and `result[1]` form.
Merge pull request #4 from Irio/fix-shift-in-macruby

Remove use of global variables to get Regexp captures in Subtitle#shift
Remove coveralls files
change version number