Apply licensing and adhere to upstream licensing requirements

Make Talon-for-Twitter license available in LICENSE file;
Copied the short form, customised Apache 2.0 License from the readme.md file into the LICENSE file, which was empty.

Meet license requirements of libraries derived from;
This has been done by including the explicit license file for each* library located in /lib and any indirectly used libraries. * the Android Open Source Project license is only included once to cover several libraries.