Move to MIT license, to go with Bootstrap 3.x

Ref: https://github.com/twbs/bootstrap/issues/2054

Thank you Ivan!
Simplify the license line so there is no potential confusion and insure compatibility with Bootstrap 3.x

The MIT license already states: "The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software."
Merge pull request #50 from marclaporte/patch-1

Move to MIT license, to go with Bootstrap 3.x