Add Ruby ERB language spec

ERB (or Embedded Ruby) is a preprocessor or templating language in common use in Ruby projects.

ERB is similar in concept PHP, and is commonly embedded within HTML files. It uses

• <% ruby code %> - this will just execute the embedded ruby code
• <%- ruby code -%> - this will execute the embedded ruby code and strip the white space from the ERB segment
• <%= ruby code %> - this will execute the embedded ruby code, and replace the ERB tag with the output from the ruby code
• <%# ruby code %> - this is a commented out section of ERB and will be removed from the file and ignored

This merge request

1. Fixes a bug in the Ruby language spec to prevent ERB closing tags being interpreted as an uncommon literal syntax in Ruby
2. Adds an ERB language spec as a default (*.erb files)
3. Adds an ERB in HTML language spec (*.html.erb files) - these are the default for view templates in Ruby on Rails projects
4. Adds an ERB in Javascript language spec (*.js.erb files) - these are used for SJR responses in Ruby on Rails projects