Avoid header generation

[kape1395]

It seems now that the hamcrest.hrl file is only generated to have all the matchers auto-imported.

Would you accept a pull-request for making that header static or for replacing the ?assertThat macros with functions that could be instrumented using parse-transform?

Use of the parse-transform would allow to avoid including the header into the user code at all. I think that could be implemented similarly, as it is done in the lager application.