style(animateSpec): remove ws
test(docs): disable brittle tests that need to be rewritten
feat(mocks): make $timeout#flush throw an exception when empty

When calling $timeout.flush with or without a delay an exception should
be thrown if there is nothing to be flushed.

This prevents tests from flushing stuff unnecessarily.

BREAKING CHANGE: calling $timeout.flush(delay) when there is no task to be flushed
within the delay throws an exception now.

Please adjust the delay or remove the flush call from your tests as the exception
is a signed of a programming error.
fix(mocks): $timeout#flush should not update time when empty

When $timeout#flush is called with a delay and no task can be flushed within that
delay, the current time should not be updated as that gets the mock into an inconsistent
state.

BREAKING CHANGE: if a tests was written around the buggy behavior the delays might be off now

This would typically not be a problem, but because of the previous breaking change in
$timeout.flush, the combination of two might be confusing and that's why we are documenting
it.

Old behavior:

```
doSomething(); //schedules task to execute in 500ms from now
doOtherStuff(); //schedules task to execute in 600ms from now

try {
  $timeout.flush(300); // throws "no task to be flushed" exception
} catch(e) {};
$time.flush(200); //flushes only doSomething() task
```

New behavior:

```
doSomething(); //schedules task to execute in 500ms from now
doOtherStuff(); //schedules task to execute in 600ms from now

try {
  $timeout.flush(300); // throws "no task to be flushed" exception
} catch(e) {};
$time.flush(200); // throws "no task to be flushed" exception again
                  // because previous exception didn't move the time forward
```

Fixed test:

```
doSomething(); //schedules task to execute in 500ms from now
doOtherStuff(); //schedules task to execute in 600ms from now

try {
  $timeout.flush(300); // throws "no task to be flushed" exception
} catch(e) {};
$time.flush(500); // flushes only doSomething() task
```
feat(Scope): async auto-flush $evalAsync queue when outside of $digest

This change causes a new $digest to be scheduled in the next tick if
a task was was sent to the $evalAsync queue from outside of a $digest
or an $apply.

While this mode of operation is not common for most of the user code,
this change means that $q promises that utilze $evalAsync queue to
guarantee asynchronicity of promise apis will now also resolve outside
of a $digest, which turned out to be a big pain point for some developers.

The implementation ensures that we don't do more work than needed and
that we coalese as much work as possible into a single $digest.

The use of $browser instead of setTimeout ensures that we can mock out
and control the scheduling of "auto-flush", which should in theory
allow all of the existing code and tests to work without negative
side-effects.

Closes #3539
Closes #2438