update mocker version to fix travis build

Looks like version 1.1 of mocker is no longer available.
Could not find a version that satisfies the requirement mocker==1.1
(from -r requirements.txt (line 4)) (from versions: 1.1.1, 1.1.1,
1.1.1, 1.1.1, 1.1.1, 1.1.1, 1.1.1)