Top level option abstractions

[mitchhentges]

Fixes #195

This also contains #213, so I wouldn't recommend reviewing until that change lands.

Improvements:

• --service-account and --credentials are now only required if --do-not-contact-google-play isn't provided
• push_apk and update_apk_description now accept types for track and connection, rather than mutually-exclusive primitive parameters
• check_rollout no longer ignores --do-not-contact-google-play

[coveralls]

Coverage increased (+0.3%) to 95.136% when pulling 006189c on mitchhentges:top-level-option-abstractions into f41ad26 on mozilla-releng:master.

[mitchhentges]

After some discussion ending here, we're not going to use types on the API boundary