Update uglify-js to 2.3
Merge pull request #103 from walmartlabs/uglify-2.3

Update uglify-js to 2.3
Fix iteration over added mixins
Merge branch 'master' of github.com:walmartlabs/lumbar
Update release notes
2.2.6
Fix mixin attribute propagation
Update release notes
2.2.7
Merge branch 'master' into amdy