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
Merge branch 'master' into common_info
switch order of pmf and outcomes
make conditioning work in common_information, and fix a test
Merge branch 'master' into common_info
Merge pull request #30 from Autoplectic/common_info

Add the Gacs-Korner common information
add two tests for coinformation