Add Rake test to run check and format commands

[wenderjean]

Closes #70

[kddnewton]

@wenderjean I think this is really good!

In terms of direction, now that I look at this, I think it's close but I'd like to change it just a bit. Could you create a CheckTask and a WriteTask? I don't think folks will want to run them together as often as they'll want to run them separately.

Also, if you could accept an optional name to the task (like the test task currently does) where it's something like:

def initialize(name = :stree_check)
def initialize(name = :stree_write)

then folks can override it if they want to.

[kddnewton]

Nice work @wenderjean!