Build: Excanvas to Bower dependency

Remove checked in copy of Excanvas with bower install.
Minor task cleanup for bower.
Build: Bump assemble version

Some people reported errors because the 0.4.4 didn't include the new
i18n additions.
Updated :tabable and :focusable filter to jQuery UI variant.
* Accommodates for more tag situations including image maps
* Adds a :focusable expression which it needed by the menu plugin
** :taxable takes into account tabindex, focusable ignores tabindex  which is required for some situations.
Updated :tabable and :focusable filter to jQuery UI variant.
* Accommodates for more tag situations including image maps
* Adds a :focusable expression which it needed by the menu plugin
** :taxable takes into account tabindex, focusable ignores tabindex  which is required for some situations.
Merge branch 'helper-focusable_tabable' of github.com:masterbee/wet-boew into helper-focusable_tabable

Conflicts:
	src/core/helpers.coffee
Merge pull request #2999 from nschonni/excanvas-to-bower

Build additions: i18n and Excanvas

Thanks @nschonni, nice addition and cleanup
Build: Add wet-boew-dist CI builds

Use a simplified version of the current post_build script for deploying
assets on Travis builds
Merge pull request #2996 from nschonni/v4-add-travis-artifacts

Build: Add wet-boew-dist CI builds
Remove travis task because of incorrect /dev/null logging
Merge pull request #3000 from masterbee/helper-focusable_tabable

Updated :tabable and :focusable filter to jQuery UI variant.