Add utils.py, move functions into it.
timing_model: add MJDParameter, fix up associated calculations.
Merge branch 'scott'
Add simple pulse phase class.
Cleaned up SPICE calls and added one from observatories.py to it
renamed and cleaned up SPICE stuff.  DO NOT USE TABS!  Or camelCase! Yuck!
Added ability to parse sci notation for MJDs.  And MJD precision.