feat(bsSwitch): switchWrapper property

Add switchWrapper propert to customize the container wrapper CSS class.
Add test for switchWrapper property.
Karma update to latest version.
Update to angular ~1.2.15.
Improve click switch test.

Note: commit based on my temporary fork of bootstrap-switch.
Update .travis.yml

Discard NodeJS 0.8
feat(wrapper): complete wrapper feature, refer to main plugin at ~3.0.0