syntax highlighting - strings - issue related to %%  #27

It seems to create multiple nested string syntax highlights... and since my theme uses a semi-transparent background for the string highlights, you can clearly see that they are piling up on top of each other because they get darker and darker throughout the file:

On closer inspection, it looks like it's related to the characters %%- and %%=.
And in case it helps, this is a .erb file, and the <%% is meant to escape the ERB tag so that it will output the <% characters for use in an underscore template.

Moved from atom/language-ruby#67