Fix #120: Highlight strings in default parameters
Fix #120: Highlight strings in default parameters

Add highlighting of strings in default parameters and nested
'parameter functions'.

guillermooo/dart-sublime-bundle,guillermooo-forks/dart-sublime-bundle,guillermooo/dart-sublime-bundle,guillermooo/dart-sublime-bundle,guillermooo-forks/dart-sublime-bundle,guillermooo-forks/dart-sublime-bundle,guillermooo-forks/dart-sublime-bundle,guillermooo/dart-sublime-bundle