Split __init__ up

The initializer was getting ridiculously large; time to split it into
manageable pieces
Removed tests for failure

The framerate and resolution properties can now be set even when the
preview is running
Fix #24

Crop's getter now works. Unfortunately the resetting of non-rectangular
zooms doesn't seem to but I suspect that's a firmware issue (what sort
of phone is ever going to let you do a non-rectangular zoom...) so
there's not much we can do about it unless we fancy deprecating crop and
replacing it with pan & zoom attributes?
Fix #25

First stab at adding the new video recording options. Needs tests and
testing
Get the changelog ready for 0.7
Prevent double exception on stop_recording()

When stop_recording() is called without a recording being in progress,
the finally clause results in a second exception being raised
Add rudimentary video tests

Add the current extremely rudimentary video tests for #8 - they're not
good enough to close the ticket yet, but at least we can tell whether or
not the recording methods crash...