Print external URL when using debug --print-only

- Using the --print-only option implies that the user is on a remote
  server, so providing a localhost URL is unhelpful.
Post MTurk HIT URL on HIT creation
switch to gnureadline
Tunnel through firewalls

- This commit adds:
  - a tunnel client
  - psiturk_tunnel module to wrap the client
  - basic tunnel commands (open, close) to the psiturk_shell
Improve tunnel commands in shell
Remove print statements from debugging
Add fuzzy match suggestion for mistyped commands
Provide tunnel URL to ad server

- Refactor Tunnel module into psiturk_org_services.py
Point tunnel at tunnel.psiturk.org
Merge branch 'tunnel' into dev
Include tunnel in fuzzy-match
stepping version in dev
add patricia's doc contributions
changing instructions to reference gnureadline
don't need a new empty directory since psiturk makes a new folder for you
tunnel needs to be in the MANIFEST.in for setuptools
Fix ngrok permission issue
Remove stat dependency
Kill tunnel processes without privilages
Gracefully handle abrupt keyboard interruptions