Tabix file access with golang using biogo machinery (library)

 Bixis a pure go tabix reader. Tabix has a minimum resolution of 16K
 bases. So, for dense annotations like ExAC, repeated queries will have to
 re-parse the same intervals. To mitigate this, Bix caches all annotations
 for the blocks from each query and re-uses them for later queries to
 the same block. In practice, this results in 10X-100X speedup for any
 type of data.