Fixing sky initialization

Updated initialization so that any --ifo arguments are accepted.

Deleted unused function detector_shifts and small code cleanups in sky_ring_proposal

See before and after: (axes are RA sindec)

assigned to @katerina.chatziioannou and @sophie.hourihane

added 6 commits

• 820f28e9...87007e5c - 2 commits from branch lscsoft:CBC
• faa765be - Minor code cleanups
• ee415171 - Fixing time prior initialization in burnin_bayescbc
• 3d74a0f3 - Adding Import Guards
• 1dce6f07 - Fixing initial sky localization

Compare with previous version

mentioned in commit 40d58eca

merged

mentioned in issue #120 (closed)