Fix gensim build (docs & pyemd issues)

[menshikh-iv]

Current PR fix our build, we have 2 issues now

1. pyemd not compiled properly when installed (sometimes) and raise numpy.ufunc has the wrong size, try recompiling. Expected 192, got 216.
   Solution: implement correct skipping if import failed
2. sphinx have some issues (related to autodoc + imports and programoutput plugins).
   Solution: extend sys.path + pre-compile binaries before build an documentation.