Added new function to create a compose repo file

Requires the repo_url be passed in the command.
Example
-------
```
fab -H ibm-x3550m3-12.lab.eng.brq.redhat.com -u root -p '******' add_repo:'test','http://porkchop.devel.redhat.com/released/RHEL-7/7.0/Server/x86_64/os/';
[ibm-x3550m3-12.lab.eng.brq.redhat.com] Executing task 'add_repo'
[ibm-x3550m3-12.lab.eng.brq.redhat.com] run: echo "[test]
name=test
baseurl=http://porkchop.devel.redhat.com/released/RHEL-7/7.0/Server/x86_64/os/
enabled=1
" >> automation-tools.repo
```
Adresses #72 
@JacobCallahan these tasks are intended to be used by an CI server. With that said, returning a non-zero return code as done by `sys.exit(1)` in other tasks ensure that the job run will fail if something is not right and will let us fix. Also will not proceed and give other strange errors.

Even though the docs will alert, the common practice over automation-tools is to fail earlier than later to avoid compromising the entire server. Will be easier to fix a unique failure and continue where it stepped manually.