Update README.txt/AUTHORS.txt

[Youw]

• add notice about moving under @libusb/hidapi;
• update links if there are any;
• consider Markdown?

[todbot]

+1 on Markdown

[z3ntu]

Notes from #17 that should be fixed as a follow-up:

• the text is now rather lengthy in comparison to original, which is more compressed. I feel the markdown version is overwhelming, what about having some table of contents in the beginning?
• Title of library is broken down into 2 lines, with "X" from OS X in second line. What about using ## heading which would results in smaller letters?

[Qbicz]

Fixed by #19

[Youw]

AUTHORS.txt hasn't been updated yet, aren't we going to?

[Qbicz]

@Youw if you have idea how AUTHORS should now look like, please go ahead with PR ;)

[Youw]

I'll think of something when I'm back from a family trip. (Somewhere next week.)