chore(build): add jscs code style check to our build

Closes #6062
fix(docs): clarify doc for "args" in $broadcast and $emit

Closes #6047.
Edited the 'Flushing HTTP requests' section

Minor grammatical edits in the Flushing HTTP requests section.
fix(filterFilter): don't interpret dots in predicate object fields as paths

Closes #6005
Closes #6009
chore(travis): remove BrowserStack credentials

Closes #5596
fix($compile): retain CSS classes added in cloneAttachFn on asynchronous directives

Previously, classes added to asynchronous directive elements during the clone
attach function would not persist after the node is merged with the template, prior
to linking. This change corrects this behaviour and brings it in line with synchronous
directives.

Closes #5439
Closes #5617
fix($q): make $q.reject support `finally` and `catch`

Add support for the functions `finally` and `catch` to the
promise returned by `$q.reject`

Closes #6048
Closes #6076
fix($http): update httpBackend to use ActiveXObject on IE8 if necessary

window.XMLHttpRequest is not always available in IE8 despite it not running in quirks mode,
in which case Angular should be using the ActiveXObject instead. Just checking the browser
version is taking too many shortcuts.

Closes #5677
Closes #5679