Cmake, travis, and others

[NikolausDemmel]

This is supposed to accompany JakobEngel/dso#109

• Add travis build check (for now against my fork, until Cmake, travis, and others dso#109 is merged)
• Add more ways to find DSO. If it is built in catkin workspace, it is picked up automatically. If not, you can still set DSO_PATH manually.
• compiler flags updated to match Cmake, travis, and others dso#109
• updated package.xml