support jsmin.py from v8
fix tests for Sass 3.4
"Merge pull request #373 from danc86/sass34\n\nfix tests for Sass 3.4"
"Merge pull request #372 from danc86/v8-jsmin\n\nsupport jsmin.py from v8"
libsass filter: Set max_debug_level.

Fixes #368.