Renamed sliding_window.py to vcf_sliding_window
Added snpwise fstat calculator
removed extra possible allele: should be 0-3 not 0-4
Removed NaNs from multilocus fstat calculations adjusting sample size appropriately.
Minor cosmetic changes.
Added hackey function to test of vcf file is gzipped. 
Preliminary vcf to bayesscan input script
Cosmetic changes.