Changed == and != operators in Time so no exceptions are thrown
Changed time testing to reflect changes in != and == operators for Time
Removed superfluous operator strings in calls to _tai_difference
Made == and != assertions more explicit
Accidentally left git marker in core.py
Changed _tai_difference to _time_difference
Fixed docstring
Merge pull request #2114 from amras1/no-time-equality-exception

Removed exceptions from == and != for Time