Vendor dependencies

Let's see how I like this workflow.

vendor/chrono/Makefile

@@ -0,0 +1,26 @@
+# this Makefile is mostly for the packaging convenience.
+# casual users should use `cargo` to retrieve the appropriate version of Chrono.
+
+CHANNEL=stable
+
+.PHONY: all
+all:
+	@echo 'Try `cargo build` instead.'
+
+.PHONY: authors
+authors:
+	echo 'Chrono is mainly written by Kang Seonghoon <public+rust@mearie.org>,' > AUTHORS.txt
+	echo 'and also the following people (in ascending order):' >> AUTHORS.txt
+	echo >> AUTHORS.txt
+	git log --format='%aN <%aE>' | grep -v 'Kang Seonghoon' | sort -u >> AUTHORS.txt
+
+.PHONY: readme README.md
+readme: README.md
+
+.PHONY: test
+test:
+	CHANNEL=$(CHANNEL) ./ci/travis.sh
+
+.PHONY: doc
+doc: authors readme
+	cargo doc --features 'serde rustc-serialize bincode'