Add file .gitignore
Add GPIO control on BeagleBoneBlack .
Add fclose() after reading the gpio value file
Add check_export_gpio() before export_gpio()
Add *.so *.o to .gitignore
Change 'SPIClass & SPI' & 'TwoWire & Wire' to board_related
Add BeagleBoneBlack uart1 uart2 uart4 support.
Add micro "BOARD_BEAGLEBONEBLACK" in uart spi wire driver
Add BeagleBoneBlack spi1 i2c1 i2c2 support.
Add debug for testing uart functions.
Merge branch 'bone_black' of ssh://172.16.5.58/home/mars/workspace/SDK/ into bone_black

Conflicts:
	lib/c/itead_serial.c
Add SDK python interface for BeagleBoneBlack
Merge branch 'bone_black' of ssh://172.16.5.58/home/mars/workspace/SDK/ into bone_black
Test uart gpio spi i2c , it's ok now.
For Beagleboneblack :
delete gpio1_21 gpio1_22 gpio1_23 gpio1_24
add gpio0_22 gpio0_23 gpio1_18 gpio1_19
for Beagleboneblack ,change i2c port
for Beagleboneblack change spi1dev to /dev/spidev1.0
Add BeagleBoneBlack ADC support.
Add BeagleBoneBlack ADC python interface.
Merge pull request #3 from guluguluchui/BeagleBoneBlack

Merge Beagle bone black into master. Add support for Beagle bone black board and provide analogRead() funciton (reference voltage = 1.8V)