Add tests for loading/filtering reads; test mdtag conversion; fix mdtag ...

This includes a fix for #119 
- #119 is due to upstream ADAM issue https://github.com/bigdatagenomics/adam/pull/339.  It is resolved here by simpling assigning a mdTag of None for reads with 101I Cigar and "0" mdtag.  For our purposes, these reads essentially have no useful mdtag information.

Other additions:
- More tests for serializing and deserializing mapped reads
- Tests for Read InputFilters
- Token field was not set properly for tumor/normal reads (it was not passed to fromSAMRecord)
- Tests for mapped vs unmapped reads