Gumstix build

When building including the CppUTest memory detection headers it overrides some memory functions resulting in errors when the library is then included in applications. This was demonstrated trying to previous building the sample application using `make sample`.

This merge includes a make toggle to enable/disable memory lead detection when building.
To build and run tests: `make clean && make BUILD=test`
To build for application use: `make clean && make`
To build and run sample application: `make clean && make sample`

This merge also adds interrupt handling to the sample application to properly exit.