chore: add script for updating bower repos
chore(travis): let's give BrowserStack a try

Switch the build to use BrowserStack instead of SauceLabs.

This also adds IE11 to our build.
chore(travis): add some more info for BrowserStack sessions
refactor(angular.js): improve trim performance

According to Flagrant Badassery's blog
http://blog.stevenlevithan.com/archives/faster-trim-javascript
and this comparison http://jsperf.com/trim-function, this trim method is faster.

Closes #4406
docs(guide/scope): access the current element's scope in the console.

Closes #4884
docs(CONTRIBUTING): fix broken link to GitHub PR Helper

Closes #5134
docs(compile): fix typo

Closes #5133
chore(changelog): remove tmp file
chore(mocks): wrap angular-mocks.js in closure

Closes #5080
fix(ngSanitize): prefer textContent to innerText to avoid layout trashing

innerText depends on styling as it doesn't display hidden elements.
Therefore, it's better to use textContent not to cause unnecessary
reflows. However, IE<9 don't support textContent so the innerText
fallback is necessary. Note that we need to check for undefine
and not just reverse the order of these two since for an empty string
innerText would still be checked and a reflow would occur.