Install bullet after ros ppa is added.
Crash if apt-get failed.
Make git quiet whenever possible.
Use the correct version of sot-pg, correct compilation order.
Update README.md

Remove reference to electric, cleanup
Correct the cloning process: directly take the branch to clone if given.

Allows avoiding issues during the checkout.
e.g. because of submodules creation/destruction.
[Travis] Correct travis.

The old version crashed after 3000 characters are written on travis.
Also, it seems impossible to redirect the output to read it
at the end of the compilation.
Finally, reduce the output of the make command in order to
fit travis output conditions (<4Mb)
Change the test for jrl_dynamics_urdf to simplify the add of new ros distro.
Merge pull request #24 from francois-keith/master

Correct compilation of sot-pg, correct travis compilation.