fix(pip): update location of pip installer

raw.github.com URLs have moved to raw.githubusercontent.com, and
wget was seeing a 301 (Moved Permanently) under the covers. curl
does not automatically follow such a redirect, so the URL change
caused an error for deis/tester, but was benign here.
docs(ec2): add CLI key import, explicit chdir
docs(rackspace): add explicit chdir
docs(ec2): add CLI key import, explicit chdir
Merge pull request #865 from deis/fix-ec2-readme

docs(ec2): add CLI key import, explicit chdir
fix(contrib/ec2): fix README from #865

There was a mistake in #865 - we want to add the pubkey for
~/.ssh/deis
Merge pull request #868 from deis/fix_865

fix(contrib/ec2): fix README from #865
refactor(Makefile): better multi-node support

Our READMEs and Makefile really fall short for multi-node setups.
Specifically, we allude to the fact that DNS records will need to be
setup, but we don't provide additional info.

This commit updates the main README, contrib/ec2, and contrib/rackspace
with specific instructions for accessing the controller and router
for multi-node setups.

Additionally, the Makefile has been refactored so that there aren't
separate paths for 1-node and multi-node setups. Now we always start
the router, as we have provided instructions regarding DNS in the main README.
fix(systemd): handle starting containers that already exist

After a reboot, named containers for Deis components often
exist in a stopped state.  Prior to this commit,
Deis would fail to start the components due to a name conflict.
Now any existing named containers are removed in ExecStartPre
so ExecStart should always succeed.
Merge pull request #871 from deis/remove-on-start

fix(systemd): handle starting containers that already exist
docs(dns): move content from README.md into "Configure DNS" doc
Merge pull request #870 from deis/dns_readme

refactor(Makefile): better multi-node support
fix(docker): add an ARP entry each time a container comes up
fix(contrib): #859 remove update manager stop commands from Vagrantfile
fix(user-data): use $private_ipv4 for etcd/fleet

All etcd/fleet communication should be private, so have etcd/fleet
only listen on private IPs. Remote fleetctl still works, as it uses
an SSH tunnel. There's really no reason to ever use $public_ipv4.
fix(contrib/ec2): use shared user-data

Previously, contrib/ec2 used its own stripped-down user-data file.
We have customizations in contrib/coreos/user-data, and we want all
providers using the same user-data file.

To do this, we introduce a Python script which will dynamically generate
the appropriate JSON payload from contrib/coreos/user-data when running
the provision-ec2-cluster script. While ideally this would be achieved without
requiring an external scripting language, this is very easy to achieve in Python,
and we already require Python as a dependency (since the AWS CLI is a Python package).

Also, have EC2 respect DEIS_NUM_INSTANCES like every other provider does.

closes #858, #826
docs(typo): change "EC2" to "Rackspace"
Merge pull request #869 from deis/contrib_use_user_data

fix(contrib/coreos/user-data): prevent reboots; use $private_ipv4 for etcd/fleet
style(coreos): remove unused systemd template strings
fix(builder): do not check for a Procfile

Some applications do not have a Procfile present before a buildpack
compile step[1]. If a Dockerfile is not present, then the builder
should make the assumption that this app is a buildpack app.

[1]: https://github.com/bacongobbler/heroku-buildpack-jekyll/blob/master/bin/release