Update Grunt dependencies and tweak build
Add TinyMCE 4 plugin for WP 3.9
Widen slider edit screen fields on larger screens
Add lsjl_slider_selector filter
Add JavaScript loading optimization option

Adds the option to not load the Flexslider script if the slider only
contains a single image, since it won't do anything anyway.
Add plugin version to asset enqueues
Tweak formatting
Update translation
Update version to 1.7.0. Update documentation.