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.
style(Angular.js): fix typo in comment
style(Scope): rename child scope type from Child to ChildScope

This change makes it easier to debug angular, especiall when dealing with heap snapshots
and hunting for memory leaks.
style(Scope): remove extra ws
docs: fixed a typo and made a minor edit to docs section of CONTRIBUTING.md
chore(karma): correct the 404 ignoring
chore(travis): use different port numbers per build

We can't establish multiple SSH tunnels for the same port (for BrowserStack).
This makes it possible to run multiple parallel builds using BrowserStack.
chore(travis): log used ports
chore(travis): report both build number and id to BS
chore(travis): define a launcher for IE11 (SauceLabs)
chore(travis): switch back to SauceLabs

I think we are pretty close to be able to use both.

The xhr-polling seems to be pretty stable, but I'm having problems with multiple SSH tunnels (on BS), so let's try to switch back to SL.
chore(travis): disable IE11

For some reason it's broken on SL.
chore(travis): set SauceLabs build id
feat(jqLite): implement the `empty` method

jQuery's elem.html('') is way slower than elem.empty(). As clearing
element contents happens quite often in certain scenarios, switching
to using .empty() provides a significant performance boost when using
Angular with jQuery.