Fix highlighting regexp literal

Original code highlights regexp wrong if another '/' is existed in same line,
such as:

   emit = emit.replace /hubot/ig, "<b>#{robot.name}</b>"

Original code treats `/hubot/ig, "<b>#{robot.name}</` as regexp literal.
Because it uses greedy matching.
Merge pull request #161 from defunkt/fix-regexp-literal

Fix highlighting regexp literal