Support for raw attributes strings

A tag immediately followed by a `{raw}` will have
`raw` inserted without escape to its attribute
string. For example: `a{"hi"}` will render
`<a "hi"></a>`.
Concatenate multiple raw attribute expressions
Double `{` raw attributes keep both `{` in output

Special handlebars case for raw attributes,
when a tag uses `a{{hi}}` doubled brackets,
both are included in output: "<a {{hi}}></a>`.
Raw attribute strings added to documentation
Raw attribute basic test cases
Typo in documentation, fixed raw attribute string title
Merge branch 'feature_raw_attribute_strings' into HEAD

* feature_raw_attribute_strings:
  Typo in documentation, fixed raw attribute string title
  Raw attribute basic test cases
  Raw attribute strings added to documentation
  Double `{` raw attributes keep both `{` in output
  Concatenate multiple raw attribute expressions
  Support for raw attributes strings
  Rename binary file to jade.js