Abstract task-syncing interface (or: refactor the things)

[wizonesolutions]

Before integrating more task managers, I need to abstract out the task-syncing logic a bit. Unless someone helps me, I'm not going to go as far as to try and be cool and make a plugin interface or something.

More like just putting the RTM stuff in its own class and maybe having a superclass with some common functions (probably not in v1).

Probably need a config file that sets the default todo-syncing service as well. And a more unified file that tracks state per service (rather than the current set of scattered files).

[wizonesolutions]

Step 1: nconf. However, the sync services should be an array because there could be several.

[wizonesolutions]

Also need to add a --setup flag for first-time authentication to the different services. I shouldn't do this on normal runs anymore because it will interfere with the asynchronous behavior.