Read Skeleton from skel file
Update Migration.md
Initialize skeleton after it is read from skel file
Add Marker::getBodyNode()
Merge branch 'origin/master'

Conflicts:
	Migration.md
Merge pull request #169 from dartsim/read_skeleton

Read Skeleton from skel file
Fix bullet linking using pkg-config and BULLET_CFLAGS

This adds a step to search for bullet using pkg-config on
UNIX systems. This is necessary to identify the CFLAGS
which are not provided by the FindBullet module.
The CFLAGS are needed to distinguish between single and
double precision sizes of btScalar.
Merge pull request #176 from scpeters/bullet_pkg_config

Fix bullet linking using pkg-config and BULLET_CFLAGS
Add Bullet collision detector installation for CI
Install libbuleet-dev for Travis-CI
Debugging contact constraint for articulated body systems
Revert "Debugging contact constraint for articulated body systems"

This reverts commit c6c2b1daa35e17c05f9b633ddfe3936278c56228.
Add Joint::getBodyConstraintWrench()

- Get constraint wrench expressed in body node frame.
- Joint::mWrench is duplication of BodyNode::mF. One of them should be removed.
Merge remote-tracking branch 'dartsim/master'
Merge branch 'master' into lizard
new optimization tested with joint stress