version conflicts are now an error

[bukzor]

killed three TODOs in the process

[asottile]

when travis is happy

[coveralls]

Coverage decreased (-0.08%) when pulling 02c5aae on conflict-is-an-error into 51a2e0f on master.

[coveralls]

Coverage remained the same when pulling 5e82a44 on conflict-is-an-error into 51a2e0f on master.

[coveralls]

Coverage remained the same when pulling e961122 on conflict-is-an-error into 51a2e0f on master.

[coveralls]

Coverage remained the same when pulling 6afbaa7 on conflict-is-an-error into 51a2e0f on master.

[coveralls]

Coverage remained the same when pulling 608e850 on conflict-is-an-error into db32501 on master.

[coveralls]

Coverage increased (+0.69%) when pulling a687bcd on conflict-is-an-error into fea9833 on master.

[coveralls]

Coverage increased (+0.69%) when pulling a687bcd on conflict-is-an-error into fea9833 on master.

[coveralls]

Coverage decreased (-0.49%) when pulling 19b4bfc on conflict-is-an-error into fea9833 on master.

[coveralls]

Coverage decreased (-0.02%) when pulling 7a922f9 on conflict-is-an-error into fea9833 on master.