Merge pull request #1 from henryaj/master

Updated to use Timecop#travel to simulate bike being out
Removed time and serial number methods
Added time and renting methods and tests (passing)
Added get_bikes_from and get_broken_bikes_from methods to BikeContainer module
Extensive refactoring of bike container methods using lambdas
Merge branch 'benjamintillett-benhenry'
Merged in changes from pairing with Ben Tillett