Add Redis its dependencies and configuration.

Summary:
Modify setup.sh to install and configure redis. setup.sh downloads
redis-2.8.17, which is the same available through AWS (Debian/Ubuntu's version
is far too old), compiles and installs it (through stow), configures it using
the utils/install_server.sh redis.io distributes.

Add Redis configuration parameters to etc/config-dev.json (nothing for
etc/config-test.json yet).

Test Plan:
Bring up a new virtual machine and make sure Redis is running by connecting
through redis-cli. Fire up the Python console and run the following piece of
code to make sure the redis pip package works correctly:

```
from redis import StrictRedis

client = StrictRedis(host='localhost')
print client.ping()
```

Reviewers: dlitz, kav-ya

Reviewed By: kav-ya

Subscribers: emfree

Differential Revision: https://review.inboxapp.com/D730