Demo scripts

[ddemidov]

I think this repo needs some examples. We can adapt some from boostc, or create something new, but it would help new users of the bindings.

E.g . see http://ev3dev.org/irclog/#id-29877

[EricPobot]

There is a basic one for motors in my fork. Feel free to pick it and adapt as you like.

[ddemidov]

@laurensvalk kindly agreed to provide simple robot instructions from his book for use with ev3dev examples: ev3dev/ev3dev#329 (comment). We could use the robot as a base for our code examples.

[rhempel]

Please review a43897f to see if this fixes the issue. I have added links to "Demo Robot" and "Demo Code" in the docs - this will be part of ReadTheDocs as well after the next release.

The resulting GitHub README.rst page is here

[bittner]

Please note the proposed directory structure for demos! Thank you.