make targets in docs/Makefile available at top level

Author: dcrosta

Makefile

@@ -1,2 +1,7 @@
-build:
-	cd docs && make html
+.PHONY: build
+build: html
+
+# this pattern rule lets you run "make build" (or any other target
+# in docs/Makefile) in this directory as though you were in docs/
+%:
+	cd docs && make $@