Missing routes for Remote-Remote

We lack direct routes to copy data between remote computers without touching the local system.

``` Python
into('ssh://A:myfile.csv', 'ssh://A:myfile2.csv') # Should be a remote local copy
into('ssh://A:myfile.csv', 'ssh://B:myfile.csv') # Should result in a remote call to scp
into('hdfs://A:myfile.csv', 'ssh://A.myfile.csv') # Should result in hadoop fs calls
into('ssh://A:myfile.csv', 'hdfs://A.myfile.csv') # Should result in hadoop fs calls
...
```

When interacting with AWS the inter-node bandwidth is very high. It'd be nice to leverage this instead of pulling down and pushing up from local.