bugfix: error when nan given as spectral type
bugfix: missing magnitude could cause exception when calculating distance
include mag lookup table
added missing equations and skeleton tests
fixed magV nan error (at end not source - needs investigating later), removed un-needed files
successfully creates the absolute magnitude dictionary in python - other lookup code doesnt work (yet)
Added the SpectralTypes class. This class takes a string input of regular spectral types and interprets the input into the class letter, number and luminosity class. Each part can then be called individually or together.

Currently this class is standalone but will probably replace the default class selection
Fixed bugs with the Spectral type Class - identified issue with multi letter classes i.e. DQ (to fix later)

bugfixes
- fixed bug where an invalid luminosity class would cause the rest to reset
- added unusual single letter classes C and S, fixed error where only the letter not the whole type would be reset on fail
- Fixed bug causing cases like M8.5 that have a decimal and no L class to fail
- fixed the spectral type case where np.nan was given as a string
Added/fixed equation to estimate magnitude with new spectral type class
fixed estimation when given a single class with no number
Merge branch 'feature/spec-type-class' into develop
Merge branch 'release/0.2.1'