Node dependencies updates

[elseloop]

We (I) were (was) behind in our (my) npm dependency gardening. This aims to fix that:

• bumps up the minimal version number on a number of packages
• removes gulp-combine-media-queries from Phoenix's dependency chain, as the module's no longer being maintained and its work is now performed by gulp-minify-css
• removes npm-shrinkwrap.json from the repo (see 19fc815 for more detail)
• removes old IE support in the gradient Sass mixin (the dependencies version bumps uncovered a bug in the mixin which in turn led to dropping IE9 support in favor of the solid color background-color fallback)
• updates the globbing paths on the js gulp task
• bumps Phoenix version number to 2.1.1

Fixes #177

[ajmueller]

@elseloop I just did a pull on the development branch and ran a production build and found that, as I saw with the project I was working on, the @media queries aren't actually getting combined. A ticket was opened on the clean-css repo for this on my behalf: https://github.com/jakubpawlowicz/clean-css/issues/687.