fix logic in testing if injection is in segment, move to injection

The previous logic testing if an injection was within the segment had a bug.

This fixes that bug and moves the check into the Interferometer.inject_signal method.

mentioned in issue #114 (closed)

This closes https://git.ligo.org/Monash/tupak/issues/114

enabled an automatic merge when the pipeline for 3be3e6d0 succeeds

mentioned in commit 2656f6af

merged