- The "multiple heads / branches" feature has now landed.  This is
by far the most significant change Alembic has seen since its inception;
while the workflow of most commands hasn't changed, and the format
of version files and the ``alembic_version`` table are unchanged as well,
a new suite of features opens up in the case where multiple version
files refer to the same parent, or to the "base".  Merging of
branches, operating across distinct named heads, and multiple
independent bases are now all supported.   The feature incurs radical
changes to the internals of versioning and traversal, and should be
treated as "beta mode" for the next several subsequent releases
within 0.7.
fixes #167