fix(ngScenario): remove redundant assignment

Closes #4315
feat($interval): add a service wrapping setInterval

The $interval service simplifies creating and testing recurring tasks.
This service does not increment $browser's outstanding request count,
which means that scenario tests and Protractor tests will not timeout
when a site uses a polling function registered by $interval. Provides
a workaround for #2402.

For unit tests, repeated tasks can be controlled using ngMock$interval's
tick(), tickNext(), and tickAll() functions.
fix(input): `false` is no longer an empty value by default

`checkboxInputType` and `ngList` directives need to have special logic for whether
they are empty or not.  Previously this had been hard coded into their
own directives or the `ngRequired` directive.  This made it difficult to handle
these special cases.

This change factors out the question of whether an input is empty into a method
`$isEmpty` on the `ngModelController`.  The `ngRequired` directive now uses this
method when testing for validity and directives, such as `checkbox` or `ngList`
can override it to apply logic specific to their needs.

Closes #3490, #3658, #2594
docs(angular.equals): fix simple typo

- JavasScript -> Javascript

Closes #4323
fix(ngTouch): add $event to ng-swipe

Existing documentation implies that an Event object should be available
as `$event` on swipe directives, which previously was only working for
`ng-click`.

Closes #4071
Closes #4321
docs(cookbook/adv_forms): simplify example

Pass the `$index` directly to the `removeContact` function, instead of
searching for it in an expensive forEach loop.

Closes #4320
fix(ngTouch): ngClick does not pass touchend event when jQuery is loaded

The trigger handler event in jqLite takes an event object as a second
parameter, but jQuery requires an array of parameters. This is causing
the touchend event to not come thtough in the click handler when jQuery
is loaded.
chore(travis): enable Firefox again

This updates karma-sauce-launcher plugin, which fixes the issue we were having (it uses the latest version of wd).

This reverts 1c18c93be138c59b5c1b73cae99cc52383272146