Draft ipcluster plugin refactoring to drop SGE requirement.

The NFS partition is used instead to be able to run:

    ipcluster engines -n numproc

on each non-master node of the cluster.
add timeout when fetching json file + simpler cluster shutdown
Use the cluster thread pool to start the engines on the nodes
static: add us-west-2 and eu-west-1 to CLUSTER_REGIONS
Trying to open missing port for the client
Better startup message + be more robust to JSON changes
cluster: fix placement group logic

Updated Cluster.create_nodes to skip placement group configuration if
the region doesnt support it.

Added new PLACEMENT_GROUP_TYPES list of instance types to static module.
These instance types can be launched inside of a placement group.
Updated Cluster.create_nodes to check whether the instance type is in
PLACEMENT_GROUP_TYPES and configure accordingly.
awsutils: add block_device_map kwarg to request_instances
add all ephemeral drives when launching instances

Generalized create_root_block_device_map to create_block_device_map with
new kwarg root_snapshot_id and num_ephemeral_drives.

The num_ephemeral_drives kwarg is 24 by default which covers all
instance types. Any types that have less than 24 ephemeral drives
available will simply ignore the rest in the block device map.

Updated request_instances() to always add *all* ephemeral drives if
block_device_map is not specified.

closes gh-202
awsutils: add virtualization to list_all_instances output
Make it possible to configure a custom notebook folder
Make it possible to restart engine, better logs, make msgpack setup explicit
Better docstrings for the stop and restart plugins
Open the controller ports for IPython 0.13.1
Update the documentation according to tests done on 0.13.1
Add section on engine restart + note on growing new engines
Better packer configuration support + updated doc
awsutils: fix custom block device mapping bug

Turns out HVM instances require the ephemeral drives to be mapped to
/dev/sdX instead of /dev/sdX1, otherwise instances fail to launch with a
Server.InternalError.

closes gh-213
closes gh-46
setup: bump dependencies to latest versions
tests: pep8/pyflakes clean-up