Merge pull request #56 from opengm/master

update from master
change warningtext
Merge pull request #226 from joergkappes/RC-2.3

change warningtext
Merge pull request #227 from opengm/RC-2.3

Changes for 2.3.0
Update ChangeLog.txt
Merge pull request #61 from opengm/master

update from master to 2.3
add empty zip-dir
Merge pull request #228 from joergkappes/master

Fix problems when downloading external source
Nesterov algorithm added. The caller is pending
smoothing strategy added
Only link against librt if on Linux, not on Apple or Windows.
minor bug fixes
add missing include cmath in visitors.hxx
Merge pull request #234 from joergkappes/master

add missing include cmath in visitors.hxx
Merge pull request #233 from chaubold/fix/combilp_mac

Only link against librt if on Linux, not on Apple or Windows.
Merge pull request #232 from homul/master

Nesterov algorithm added. Caller for it is still pending
Merge pull request #62 from opengm/master

update from opengm:master
 fix bug in astar
Merge pull request #235 from joergkappes/master

Fig AStar bug
Merge pull request #1 from opengm/master

getting updates from master repo