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
Merge branch 'master' of https://github.com/angular/angular.js