Bump master branch to 4.0 and add cmake config version files
Remove one of the cmake version config files since they're identical
Use WriteBasicConfigVersionFile instead of simbody template
Merge pull request #151 from dartsim/master-4.0

Bump master branch to 4.0 and add cmake config version files (#150)
Parse joint damping from urdf files
Clean up API for contact forces
SIMBICON for Atlas robot
Remove duplicated mesh files for Atlas
Add World::removeAllSkeletons()
- Take testBuilding apart a test pertain to World class and create testWorld for it
- Add unit test for this function to testWorld
Add Migration.md and Changelog.md (template)
- We have wiki page for Version history (https://github.com/dartsim/dart/wiki/Version-history) but we need this file because:
-- The version history should be managed with commits (or pull requests) to match with them
-- Seperate contents (migration and changelog) might more clear to the user depending on their use cases
Add nlopt optimizer
Add nlopt dependency setting for CPACK, Travis-CI, and debian packaging
Build and install nlopt from source in Travis-CI test

The Ubuntu version of Travis-CI is 12.04 LTS but debian package for nlopt is not deliverd in the version.
Try to build nlopt in Travis-CI
Add reference for the optimization example problem
Try to build nlopt in Travis-CI
Try to build nlopt in Travis-CI
Try to build nlopt in Travis-CI
Remove custom cmake keyword

build_warning --> message
Add -fPIC build option for nlopt