Merge pull request #1 from Snigelson/master

[interrupt] Fixed typo (replaced + with =)
Merge pull request #2 from Snigelson/master

Interrupt related fixes
Merge pull request #3 from Snigelson/master

Latest changes from Snigelson
Updated Makefile to link to GCC Embedded Processors toolchain.

See: https://launchpad.net/~terry.guo/+archive/gcc-arm-embedded
Updated Makefile to automatically find libraries

Linking is now done using the compiler, passing map file to linker.
README was also updated to reflect changes.