AUI-1373 Use a getter instead of a setter for the AUI affix's offsetTop attribute, like offsetBottom

Signed-off-by: Henrique Vicente <henriquevicente@gmail.com>
AUI-1371 Prevent Yeti from running tests inside of "bower_components" folder
AUI-1370 Add ability to set an event's border color, style, and width
AUI-1368 Modal can't be hidden if destroyOnHide is false

I noticed that if the destroyOnHide attribute is false on the current version of the modal, the modal is never hidden. That probably happened when switching to bootstrap3. Fixed the css to properly hide the modal.

I noticed then that when showing the modal again it wouldn't be properly aligned. That's because bootstrap uses relative position for .modal-dialog, but we need it to be fixed so we can spefify where it will show up. Fixed that as well.
AUI-1328 Move "lint" task from Grunt to Gulp
AUI-1328 Move "init" task from Grunt to Gulp
AUI-1328 Move "format" task from Grunt to Gulp
AUI-1328 Split Gulp tasks into separated files
AUI-1328 Move "watch" task from Grunt to Gulp
AUI-1328 Move "test" task from Grunt to Gulp
AUI-1328 Move "build" task from Grunt to Gulp
AUI-1328 Move "api" tasks from Grunt to Gulp
AUI-1328 Move "create" tasks from Grunt to Gulp
AUI-1328 Move "cdn" tasks from Grunt to Gulp
AUI-1328 Move "release" tasks from Grunt to Gulp
AUI-1328 Use the bower-cli instead of the gulp-bower wrapper

Reason:

When running the gulp-bower (with the dependencies already installed) it takes ~10s
When running the bower-cli (with the dependencies already installed) it takes ~400ms
AUI-1328 Source formatting
AUI-1328 Source formatting
AUI-1328 Source formatting
AUI-1328 Add gulp format-img subtask