DOC: Updated example notebooks to use new Client creation

[TomAugspurger]

Creating a Client with no arguments will automatically set up a scheduler and worker processes.

http://distributed.readthedocs.io/en/latest/quickstart.html#setup-dask-distributed-the-easy-way

[coveralls]

Coverage remained the same at 74.61% when pulling 4f7c370837cf79ba0a77646cfaa94ef40f2f8085 on TomAugspurger:client-setup into 59ef0d665109b3c297484954e1dcd99f68151ea8 on dask:master.

[mrocklin]

We probably don't want to do this. Instead of creating a cluster for just this notebook we want to connect to the multi-node cluster that dask-ec2 has already set up for us.

[TomAugspurger]

That's pretty obvious in hindsight :) My bad.