Gulp-sass -> node-sass Version Is Unsupported on Node 6.1.x

[mikejr83]

The gulp-sass version pulled in uses node-sass is 3.4.2. This is is unsupported in Node 6.

This causes the failure of the package to install and thus any dependant packages, angular-strap, will fail as well.

The version should be bumped to at least 3.7.0 for node-sass. It looks like the minimum for gulp-sass will be 3.0.0 It looks like going to gulp-sass 3.1.0 is advisable. Support for all versions of node will be achieved.