Added Makefile to run tests and clean up after

Makefile

+.PHONY: clean
+clean:
+	rm *.itp* *.gro* *.dat* *.json* *.xtc* | true
+	rm -r *.ff | true
+
+.PHONY: test
+test:
+	py.test test/
+
+.PHONY: check
+check: test

clean.sh

-rm *.itp* *.gro* *.dat* *.json* *.xtc*
-rm -r *.ff