3.1.2

Main changes:

• Improves Py3 compatibility (Python 3.6 recommended for full compatibility with ete_toolchain pkg)
• Python 2 support dropped (i.e. new fixes and changes are not considering Python 2.7 compatibility)
• Fixes NCBI Taxonomy problems parsing the latest DB versions
• Added function for cophenetic matrix
• Other small bug fixes

Most important commits:

7a1f0c5 Fixes #469 NCBI db update crashes due to nocase duplicate synonyms
7597af3 ncbi_query get_topology does not break when some taxids are not found.
7914155 get_midpoint function does not return None when tree already rooted at midpoint. Returns first child instead
6cad2f7 Merge pull request #452 from etetoolkit/mca_method_issue_398
59dea1b clean up code for Python3
465f56f if the same node is provided as first argument to get_common_ancestor, returns itself. Unittest of get_common_ancestor improved.
98e255f Merge pull request #450 from dengzq1234/instance#436
1324f66 read synonyms table in get_descendant_taxa() if taxid deprecated #436
766f211 Merge pull request #449 from dengzq1234/instance#428
0b84a2a disables python 3.4 travis test
3f20592 Merge pull request #447 from dengzq1234/instance#416
437efd9 Merge pull request #446 from dengzq1234/instance#443
c639381 Merge pull request #355 from linsalrob/master
337647f Merge branch 'master' into master
b524047 Merge pull request #442 from dengzq1234/master
efbc215 Merge pull request #412 from matsen/master
068df09 Merge pull request #405 from davidhwyllie/master
573bb71 updates unitest to check sos_thr and bug #404
b345501 fixes bug when sos_thr > 0 in spoverlap get_my_evol_events . Fixes #404
1752154 Resolve long tree string problem on Windows #258
6f3d59c Merge pull request #400 from fransua/master