Updated `tagParser` regex to match calls to `_this.<tag>`

Functions with fat arrow are mapped to `_this.<tag>` in resulting js code.
e.g. using `['user1', 'user2'].map (user) => (@div null, user)` code in `render`
Merge pull request #1 from evidenceprime/fat-arrow-tag-parser

Updated `tagParser` regex to match calls to `_this.<tag>`