Added a feature to require all dependencies when calling find_package()
Addressed comments
Merge pull request #19 from ethz-asl/feature/require_all_dependencies

Added a feature to require all dependencies when calling find_package()
Updated the documentation to describe the feature
Merge pull request #20 from ethz-asl/feature/require_all_dependencies

Updated the documentation to describe the feature.
Merge pull request #1 from catkin/master

Pulling in changes from catkin