Vendor dependencies

Let's see how I like this workflow.

vendor/serde/Cargo.toml

@@ -0,0 +1,67 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+rust-version = "1.13"
+name = "serde"
+version = "1.0.151"
+authors = [
+    "Erick Tryzelaar <erick.tryzelaar@gmail.com>",
+    "David Tolnay <dtolnay@gmail.com>",
+]
+build = "build.rs"
+include = [
+    "build.rs",
+    "src/**/*.rs",
+    "crates-io.md",
+    "README.md",
+    "LICENSE-APACHE",
+    "LICENSE-MIT",
+]
+description = "A generic serialization/deserialization framework"
+homepage = "https://serde.rs"
+documentation = "https://docs.serde.rs/serde/"
+readme = "crates-io.md"
+keywords = [
+    "serde",
+    "serialization",
+    "no_std",
+]
+categories = [
+    "encoding",
+    "no-std",
+]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/serde-rs/serde"
+
+[package.metadata.playground]
+features = [
+    "derive",
+    "rc",
+]
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies.serde_derive]
+version = "=1.0.151"
+optional = true
+
+[dev-dependencies.serde_derive]
+version = "1.0"
+
+[features]
+alloc = []
+default = ["std"]
+derive = ["serde_derive"]
+rc = []
+std = []
+unstable = []