Fixed signed-unsigned comparisons
Merge pull request #265 from broadinstitute/intel_signed_comparison

Fixed signed-unsigned comparisons
README: Add IssueStats badges
Modified convert_data_to_integer and convert_data_to_float so that vector_end and missing values
are correctly handled for INT8 and INT16 types. Since vector_end is
(INT8_MIN+1) while missing is (INT8_MIN), check if the dereferenced
value is <= vector_end. If yes, handle as special case and return
INT32_MIN+1 or INT32_MIN.

Updated test case for checking bcf_*_missing values. Added line in vcf
and bcf files with missing values in many fields
Minor edits - comments, removed FIXME, fixed copy-paste mistake