Merge pull request #17 from opengm/master

update from master
Merge pull request #18 from opengm/master

update from master
Merge pull request #101 from homul/master

bug fixes for a negative objective value and computing tree agreement
Merge pull request #102 from joergkappes/master

update
Merge pull request #9 from opengm/master

pulling new updates to fix a bug