Read from position 0 of value file.

Otherwise this results in a EOF error on all but the first read.
Compare gpio value with '0' as opposed to 0

Reading the value file returns a 1 char string, not an integer.
Pause after exposing pin.

The gpio driver un Raspbian creates the gpio subdir with root-only
permissions, and then shortly afterwards updates these to allow
access to the gpio group.

Without this delay, opening a pin fails with a permission denied error
unless run as root.
Merge remote-tracking branch 'origin/gpio_reading_fixes' into working_master
Merge branch 'pause_after_pin_expose' into working_master
Add mock_gpio using gomock
Added all the pins for Raspberry Pi rev 2

see http://elinux.org/Rpi_Low-level_peripherals
Changed import path after fork
Pull-Up and Pull-Down support for the RPi
Merge commit '2adc55543b3c730510515c331dfac25e108c10d7'

* commit '2adc55543b3c730510515c331dfac25e108c10d7':
  Added all the pins for Raspberry Pi rev 2
  Add mock_gpio using gomock
  Pause after exposing pin.
  Compare gpio value with '0' as opposed to 0
  Read from position 0 of value file.