Update examples/led_remote/led_remote.pde

Line 172 was using button_pins instead of led_pins.  This caused leds to be lit dim when set to HIGH.  Changed to correct var.
Merge pull request #16 from RWSDev/master

Updated led_remote example to use correct var on line 172
Add isValid
High Speed Data Transfers/Optimization

Changes:

- Enable PTX at radio begin, in standby-I mode
- Enable PTX at radio stopListening(); in standy-I mode

- Radio startListening
- removed delay. What is there to wait for when the radio will just be
listening anyway?

- Radio powerUp
- radio will need to be powered up after configuration
- radio will not power down unless instructed to
- need to issue radio.txStandBy(); when finished transmitting to engage
standby-I mode

- Added txStandBy() to drop to standBy-I mode if not switching to RX
mode

- Radio Write: Sped up
- radio previously did not use standby mode effectively, after TX
sending of each packet, the radio is
powered down introducing a 1.5ms delay in addition to the 130us delay
from standby.
- No observe-tx code, a simple NOP cmd is sent to get the status info
- No millis() timeout, hanging condition should only occur because of
faulty code
- Simplified whatHappened() code
- Flush TX FIFO if MAX_RT met as lib does not support re-transmit
instead of flush every time.
- Remove ack size monitoring
- No powerdown needed,

- Added writeClear() function for writes that need the interrupt flags
cleared (ack payloads, etc). Same as write() otherwise

- Radio startWrite: Sped up
- Enable PTX mode is now done in stopListening() code. Enter TX mode by
writing CE high.
This brings the data transfer capabilities up to a reasonable level
- No need to power up, already in Standby-I mode
- No need for delayMicroseconds() in write functon.
- No need for delay after writing CE high
- Does not enter Standby-I mode be default. It is up to the MCU to call
the new txStandBy() function to enter standby-I mode from PTX if not
switching back to PRX

- Radio available:
- Now checks the FIFO buffer instead of the interrupt flag (no missed
data)
- Moved clearing of interrupt flags to Read()

- Radio read:
- No longer returns any value - use available to check for more data

- Radio isAckPayloadAvailable() now checks the FIFO directly

- Radio getDynamicPayloadSize() - Per the datasheet, added fix to flush
corrupted packets
Update readme temporarily

- advisory of non-compliance with current documentation
Changed writing modes

- Changed writeClear to the default radio.write() option
- Changed write() to writeBlock() - uses the auto-retry functionality of
the chip and will block forever until successful
Added writeFast() cmd - fill FIFO or return 0

- WriteFast allows the FIFO buffers to be filled up before returning 0
- The current payload will be dropped, and the previous payload resent
- The user should just keep trying to send the same data if a 0 is
received
- Slight modification to reUseTX cmd

- put the CE HIGH, LOW changes in the cmd for non-internal use
- Put the clearing of MAX_RT in the reUse cmd for non-internal use
- Removed unneeded delay from writeBlocking()
Inspired idea to change TX standby code

Realised that data would be lost if dropping to standby or power down
mode before the FIFO is empty.
txStandby now returns a boolean value to indicate whether the
transmission is complete. If there is data in the TX FIFO the radio will
not drop out of TX mode. eg: while(  !txStandBy()  ){}
Updated readme and h file for doxygen

See http://tmrh20.github.io/RF24/class_r_f24.html for the class
documenation.
Corrected part of the documentation
Updated some examples to show the new lib usage

Updated GettingStarted, pingpair, added medium speed version of transfer
rate test
Fix: Standby after regular write cmd

Realized that the normal write command should always drop to standby-I
mode immediately since the FIFO cannot be filled using this method, and
TX will be complete.
Fixed link
Fix: txStandBy hang. Updated Transfer example

- txStandBy was hanging if the last of the data timed out. Now clears
the MAX_RT flag if timed out
- Finished updating example file Transfer.ino for demonstrating
half-rate transfers using the FIFO buffers
Lib now passes all tests

Added back original startWrite function for when users want to use
manual methods. The library uses startFastWrite for its internal
functions. Provides compatibility with prev. code while still using the
new methods for everything else.
txStandby() function modified completely

txStandBy() now either works in two modes. The main mode will block
until success or fail. Using txStandBy(1) will block and retry forever
until succesful. Using a while loop with the function is no longer
required. See the updated class reference at
http://tmrh20.github.io/RF24/class_r_f24.html
Forgot to move startFastWrite to public

for use in wireless audio sketch, needed to move startWrite() to a
public function
Extended timeouts, txStandBy changes

- For use in noisy or low signal scenarios
- Allows user specified timeout period of extended duration
- Modified txStandBy() and writeBlocking() functions to rely on a user
defined timeout period, automatic retries and payload reUse
Fix: Ext. timeout hang, examples, board support

- Initial support for Due and ATTiny boards
- Fix for 0 timeout period causing hang
- Remove unnecessary delays from startWrite
- Cleaned up/Updated example files
- Optimization is nearing completion