add the common information
remove an unnecessary copy
add dit.abc
make K() allow for conditioning
update tests
add another test
update docstring
Merge branch 'master' into abc
add the total correlation
Merge branch 'master' into abc
Merge branch 'master' into common_info
switch to using coinformation for I
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
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
improve coverage of total correlation