Update readme for RF24 RPi/Arduino code merge

Update install info
Correct readme for RF24 core lib install on RPi

Error from RPi/Arduino code merge
Python wrapper for RPi added
Merge pull request #27 from mz-fuzzy/master

Python wrapper for RPi added
Fix RF24NetworkHeader::toString() and remove commented out line

- Fix RF24NetworkHeader::toString so it can work with non-print-able chars

- Remove [commented out] line that has been moved a few lines below:
    // First, stop listening so we can talk.
    //radio.stopListening();
Merge pull request #30 from flavio-fernandes/master

Fix RF24NetworkHeader::toString() and remove commented out line
Working state.
Change byte to uint8_t.