Update `include` for local search path

[rngtng]

Just a lite change to make the lib usage more flexiable:

By using #include ".." instead of #include <..> the local search path is respected as well, which allows the lib to be used in a local project folder too.

[rngtng]

btw. good a explanation on the difference I found here: http://www.deviceplus.com/how-tos/arduino-guide/arduino-preprocessor-directives-tutorial/

[lasselukkari]

Thanks!