typo
first pass at dealing with no Internet access (Issue #65)

- enables new command line option 'psiturk -c' or 'psiturk --cabinmode' which runs psiturk in a more limited, local development mode
- all the network-aware commands are removed from the shell avoiding the need to add tons of network access tests everywhere
- basically can start/stop server and do 'debug'
- not sure how to handle DB setup... if your config file points to a network mysql resource might need error message or something
- works by created a "core" PsiturkShell() class which is extended via inheritance and a few overrides by PsiturkNetworkShell()
- cabins can be in the woods or in an airplane
checks that config.txt compatible with running offline

- checks that database is using sqllite rather than mysql (although mysql could in theory access a local mysql DB, in principle seems simpler to recommend "development" mode use the local sqllist db
- checks that server host is set to localhost (works even when offline/no ip)
- otherwise prints a suggestion about how to fix these things and quits.

note: it might be more user-friendly to change these things temporarily for the user but i'm hesitant to go around changing people's config.txt file without them actually requesting it via the command line.  perhaps better to help people understand and change it themselves.
remove network requirement for 'status' command (closes Issue #65)

- cabin mode commands all seem to not need network access now
- moved local db commands (network agnostic) into PsiturkShell class
- updated do_help to work correctly for PsiturkNetworkShell
- PsiturkShell inherits from object allowing super-class method calls in PsiturkNetworkShell
- updated README
Merge remote-tracking branch 'origin/cabin-mode' into dev

Conflicts:
	psiturk/psiturk_shell.py