Add readme for python wrapper

- Add readme for python wrapper
- Add link to main page of documentation for python.
Add new RPi installer info to readme

New RPi install script available at
http://tmrh20.github.io/RF24Installer/RPi/install.sh
Fix: RPi memory corruption

- Per #46 the read_payload() function was over-reading data into the
user provided buffer
Update readme for installer

- remove sudo from installer instructions, to prevent the cloned
dirs/files from being downloaded as root
- Add D option with example info
Adding SPI enum to RPi python wrapper
Merge pull request #50 from mz-fuzzy/pyRF24fix

Adding SPI enum to RPi python wrapper per #49
Update many of the example files

- Updated gettingStarted examples to demonstrate proper pipe/address
handling by assigning a unique id to each node
- Updated gettingstarted_call_response to demonstrate 'proper' use of
ack payloads
- Added gettingstarted_handling_data example
- Added pingpair_irq_simple to demonstrate bidirectional communication
via interrupts
- Updated standard pingpair_irq example
- Use Serial.println(F()); instead of printf
Add changes from doc update
Fix mistake in example update
Merge remote-tracking branch 'origin/master' into Updates
Enable hardware warnings by default on linux

- Enable warnings by default on linux if the radio is not responding
- Revert reduction in SPI speed pending further testing
Update python readme and example

- Added more detailed setup information
- Clarified the user config portion of the example python sketch per #49