gat-1.3.4

This is a bugfix release to ensure python 2/3 compatibility.

GAT v1.3

• GAT now works under python 2 and python 3
• #3: gat-compare iterates now over shared tracks, not just the
  'merged' track.
• #2: do not split isochore in chrom.iso if isochore is "."

Gat v1.2

Minor bugfix release