Uses Arduino's avr-objcopy on system that does not ship a native one

Some systems (like OS X) does not ship a native objcopy utility, hence
CMAKE_OBJCOPY is empty arduino-cmake rules need it to be set. However
arduino's SDK does ship one. In case the system does not have one,
this patch will look for the arduino's one and ensure that
CMAKE_OBJCOPY is set to that one for the project.
Fix for libraries that do not have a .h file that matches directory name
Fix to support multiple local arduino libraries (ie libraries added with link_directories() directive)
Added vars for FindBinutils

Added setting of _CMAKE_TOOLCHAIN_PREFIX and _CMAKE_TOOLCHAIN_LOCATION
removed <...>/bin from CMAKE_SYSTEM_PREFIX_PATH

I think that <...>/bin isn't required for system prefix path. When I run without this change I get binutils from /usr/ instead of ARDUINO_SDK_PATH
Merge pull request #78 from atuleu/fixes-77

Uses Arduino's avr-objcopy on system that does not ship a native one
Merge pull request #82 from getSurreal/getsurreal

Fix for libraries that do not have a .h file that matches directory name
Merge pull request #84 from szaffarano/master

Fix for issue #83
Merge pull request #85 from cheshirekow/master

Added vars for FindBinutils
Update README.rst

Added latest contributors to README!
Merge pull request #1 from queezythegreat/master

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