initial implementation of computeMoon
dummy test to run computer barycenter
Implemented mean anomaly to true anomaly to reduce error
found earth position, added perifocal To equatorial adjustment for converting to Cartesian
sun and moon transformed to earth J2000 frame
adjusted time from TAI to TDB
clean-up and comments
replaced old computeSunPosition
corrected reference frame
Relocated axes transform of sun and moon position so the spec passes.
Merge remote-tracking branch 'agi/master' into computeSun
added to spec so that it includes tests from old computeSunPosition spec.
Horizon culling cleanup.

Mostly to match the forthcoming blog article.
Merge remote-tracking branch 'origin/master' into horizonCullingCleanup
improvements to date conversion function
cleanup some declarations
Fix to properly check for undefined values
Fix formatting for define
Fix to properly check for 'undefined'
Fix to properly check for 'undefined' and default value initializations
cleaned up comments
removed unnecessary allocations