Bug fix pyerfa requirement not being specified in setup.py

Add pyerfa requirement >=1.7.3

Bug fix and add warning to reflected light code

1. Query Horizons using TDB JD float instead of using Astropy Time Object
2. Add a warning based on the target name queried from Horizons. Can use this to help troubleshoot if the correct target was queried, especially in light of the majorbody/smallbody ambiguity.

Deprecate warning message and astropy.erfa

1. Remove print message for warning in reflected light calculations. Instead use standard warning variable.
2. Use separate erfa package instead of astropy.erfa

v0.4.1 - Deprecate leap update keywords

PR #42

v0.4.0 - Use Astropy leap seconds

Described in Issue #40

v0.3.7 - minor formatting changes

Reshape output of JPL Ephemeris call through astropy get_body_barycentric_posvel()
Change function name for JDUTC_to_SolarEmissionTDB to JDUTC_to_HJDTDB
Minor formatting

Include a new function to calculate time of emission for Solar RVs

Add a new function JDUTC_to_SolarEmissionTDB() to convert the JDUTC time of observation to the TDB time scale time of emission from the Solar center.

Also include this in the unit test and run_sample().

v0.3.5 - minor bug fix

In response to PR #37. Bug with np.size(JDUTC) for updated versions of Astropy / Numpy.

BugFix: Allow leap_update = False for SS barycentric correction

For the case of solar system barycentric corrections, leap_update flag is not propagated.

Minor changes to leap update and warning propagation

Merge pull request #35 from shbhuk/Minor-bug-warnings

Warnings not propagating