Add support for escaped mustaches
Port a fix to ID parsing
Add lexer and parser support for @data values
Add @data and escape char ("\") highlighting
Add support for single quotes strings in staches
Add support for block comments

Add support for block comments and enhance comment lexing to enable
highlighting of unclosed comments
Add support for path partial names

Add support for path partial names, which also involves having a
dedicated token for partial names (which may come in handy in the
future for looking up partial definitions)
Add negative number literal support
Remove accidentally added image
Add highlighting for new PARTIAL_NAME token
Merge pull request #46 from dmarcotte/lexer-updates

Update for recent Handlebars features/syntax