allow loading of Debug builds
fix non-string sourceMap option, fixes #337
Merge pull request #374 from rvagg/maps-fix

sourceMaps non-string option while sourceComments='map' causes crash
Code: Rescue from throwing. (#362)
Merge pull request #366 from am11/master

Code: Rescue from Segmentation Fault (#361)
Merge pull request #367 from am11/issue-362

Code: Rescue from throwing (#362)