add the common information
remove an unnecessary copy
make K() allow for conditioning
update tests
add another test
update docstring
Merge branch 'master' into common_info
Sample space is no longer the Cartesian product of alphabets.
Also, initialization takes outcomes first then pmf now.
Missed a few more unit tests and sample_space modifications.
Make non-Cython travisCI environments test first.
Fixing bad call to copy().
Merge pull request #28 from chebee7i/samplespace

Sample spaces and rearrange order for initialization.
Merge branch 'master' into abc
Merge branch 'master' into common_info
switch order of pmf and outcomes
make conditioning work in common_information, and fix a test
Add a test for sorting sigma-algebras.
Convert len_cmp -> lexico_key.
Merge pull request #29 from chebee7i/lexico_key

Use key instead of cmp for sorting.
Merge branch 'master' into common_info