LoFreq version 0.6.0 released

Changes:

• New option --cons-as-ref for cases where you want to call a consensus
  base per position and then call SNVs against it instead of calling SNVs against
  the given reference
• Default Bonferroni factor reverted to auto instead of auto-ign-zero-cov
• Removed Biopython dependency
• Added CONSVAR INFO field to vcf for denoting majority changes with regard to the reference base
• User supplied CFLAGS and LDFLAGS are passed down to Python's extension build as well