Added stuff to Makefile to run integration tests

It will run automaticly when it's a travis cron job and as well
locally when you run: make integration

Makefile

@@ -1,3 +1,4 @@
+TRAVIS_EVENT_TYPE ?= push
 EMACS ?= emacs
 CASK ?= cask
 
@@ -14,6 +15,10 @@ test:
 unit:
 	${CASK} exec buttercup -L . tests/unit/
 
+	@if [ "$(TRAVIS_EVENT_TYPE)" = "cron" ]; then \
+		${MAKE} integration;                      \
+	fi
+
 # Run all tests in tests/integration/
 integration:
 	${CASK} exec buttercup -L . tests/integration/