Remote command execution fixes

1. Updated the UI which looks more intutive while adding remote command with ssh key or password. Gives proper error if ssh key and password both are not entered.
2. Added an extra tab for "Remote Host" in the task.
3. Removed uneeded commands and fixes based on Travis's feedback.
4. Added stderr logging, earlier it was just logging stdout.

I tried ti squash all my commits in one and send a pull request but I think I messed up something. Will try to send a better pull request next time :)

I am still investigating a problem where long running jobs (>2hr) are complete but dagobah says its still running. I am not sure if its a problem with dagobah or the command I am running. Will get back to this problem in a day or two.