Add munit for unit testing.

Main method extracted to separate file to make it easier to test the _rest_ of the code.
munit is added as a submodule by running `cd src; git submodule add https://github.com/nemequ/munit.git` .

Unit testing has so far only been tested on ubuntu.

src/test/testrunner.c

@@ -0,0 +1,23 @@
+#include "testrunner.h"
+#include "test_handler.h"
+
+static MunitSuite suites[] = { 
+  { "/handler.c", handler_c_tests, NULL, 1, MUNIT_SUITE_OPTION_NONE }, 
+  { NULL, NULL, NULL, 0, MUNIT_SUITE_OPTION_NONE }
+}; 
+
+static const MunitSuite test_suite = {
+  (char*) "",
+  /* The first parameter is the array of test suites. */
+  NULL,
+  /* The second an array of suites to trigger from this one */
+  suites,
+  MUNIT_SUITE_OPTION_NONE
+};
+
+int main(int argc, char* argv[MUNIT_ARRAY_PARAM(argc + 1)]) {
+  /* Finally, we'll actually run our test suite!  That second argument
+   * is the user_data parameter which will be passed either to the
+   * test or (if provided) the fixture setup function. */
+  return munit_suite_main(&test_suite, (void*) "µnit", argc, argv);
+}