crashes when domain is included

This is a bit silly because we aren't expecting it to happen but we should prevent it regardless

```
vagrant@vagrant:~$ chacra/bin/chacractl binary delete https://chacra.ceph.com/binaries/calamari/1.4.0-rc15/centos/7/x86_64/calamari-server-1.4.0-rc15_6_gf2cad5f.el7.centos.x86_64.rpm
Traceback (most recent call last):
File "chacra/bin/chacractl", line 6, in
main.ChacraCtl()
File "/home/vagrant/chacra/local/lib/python2.7/site-packages/chacractl/main.py", line 37, in __init__
self.main(argv)
File "/home/vagrant/chacra/local/lib/python2.7/site-packages/chacractl/decorators.py", line 68, in newfunc
return f(*a, **kw)
File "/home/vagrant/chacra/local/lib/python2.7/site-packages/chacractl/main.py", line 80, in main
parser.dispatch()
File "/home/vagrant/chacra/local/lib/python2.7/site-packages/tambo/dispatcher.py", line 21, in dispatch
return instance.main()
File "/home/vagrant/chacra/local/lib/python2.7/site-packages/chacractl/api/binaries.py", line 135, in main
url_part = self.sanitize_url(self.parser.get('delete'))
File "/home/vagrant/chacra/local/lib/python2.7/site-packages/chacractl/api/binaries.py", line 50, in sanitize_url
url = url_part.lstrip('/')
```