Add AbortAndRestart example

A small example handler that demonstrates the AbortAndRestart
functionality.

It creates and runs an Async with a payload function that has a 50%
chance to throw an AbortAndRaise Exception or complete successfully.
Add further explanation to abort_and_restart example
Fix the broken batcher example

The CAS needed to do a gets instead of get. Also needed to check to do an add
first as the cas will fail if the key doesn't already exist.

Also fixed a syntax bug in the javscript portion of the template.
Merge pull request #50 from beaulyddon-wf/fix_batcher_example

Fix the broken batcher example
Merge branch 'master' into abort_and_restart_example

Conflicts:
	example/__init__.py
Merge pull request #45 from tannermiller-wf/abort_and_restart_example

Add AbortAndRestart example
Merge branch 'master' of git://github.com/WebFilings/furious