Add license information to source, GitHub repo

[commonsguy]

I see that on this library's Web page on loopj.com you state that it is licensed under the Apache License 2.0. However, your source code does not appear to have the copyright and license notice requested by the license terms. Based on the source code alone, it would appear that nobody has any rights to use the source. I suggest just adding the copyright-and-license boilerplate (tailored for you and the year) to the source files.

Also, you might consider mentioning the license in the repo's README.