Merge pull request #254 from peplin/test-suite-and-ci

Add an automated test runner for example programs and Travis CI integration
Add note about test suite in changelog
Rearrange items in changelog
Add the built status button
Add a note about unit test cases in contributing notes
Document CFLAGS, CXXFLAGS, ASFLAGS and CPPFLAGS.

After understanding the difference between CXXFLAGS and CPPFLAGS, this
is a revised commit for https://github.com/sudar/Arduino-Makefile/pull/257
Merge pull request #263 from peplin/document-flags-vars

Document CFLAGS, CXXFLAGS, ASFLAGS and CPPFLAGS.
Preserve original source file extension in object file.
Add a few new flags used in the 2014 releases of chipKIT build tools.
List linker scripts at end of LD to make sure dependencies are in order.
Add new assembly files for chipKIT startup.
Update test suite to latest MPIDE.

Almost fixed https://github.com/sudar/Arduino-Makefile/issues/253
but for https://github.com/sudar/Arduino-Makefile/issues/255
Fix URLs and installation of MPIDE when bootstrapping in OS X.
Merge branch '255-original-file-extension-in-objfile' into 253-update-mpide