Implement semi-Bayesian block model inference

This includes code for expectation maximization with belief propagation
for the stochastic block model.
9 jobs for master
Status Job ID Name Coverage
  Test
passed #1276
amd64
job_clang_amd64

06:23:23

passed #1280
amd64
job_clang_amd64_nosh

06:02:29

passed #1278
amd64
job_clang_py2_amd64

06:23:13

passed #1273
i386
job_gcc_386

09:13:02

passed #1275
amd64
job_gcc_amd64

05:31:48

passed #1279
amd64
job_gcc_amd64_nosh

05:36:56

failed #1281
i386
job_gcc_py2_386

04:59:54

passed #1277
amd64
job_gcc_py2_amd64

05:13:18

failed #1274
i386
job_gcc_py2_386

07:19:16

 
Name Stage Failure
failed
job_gcc_py2_386 Test There is an unknown failure, please try again
Doctest summary
===============
828 tests
1 failure in tests
0 failures in setup code
0 failures in cleanup code
build finished with problems, 121 warnings.

ERROR: Build failed with: exit status 1