added pifacedigital util to access pifacedigital from command line
updated docs
added git ignore
Update README.md
pifacedigital util now works correctly
Merge branch 'master' of https://github.com/piface/libpifacedigital
remove print statements
Added interrupt support, including GPIO interrupt export to userspace and blocking input read method.  Commented example program and included simple example efficient wait for input method.
Moved interrupt support to mcp23s17 library in order to facilitate sharing with PiFace Control & Display module or other mcp23s17 based systems.  Added method to allow users to disable interrupts.
Merge pull request #2 from scm6079/master

Added interrupt support with enhanced & commented example
updated version numbers and todo list
updated docs to latest version