Merge pull request #111 from pgimalac/add_readme_on_crates_io

add readme in cargo.toml to have it displayed on crates.io

Author: sdroege

Cargo.toml

@@ -6,6 +6,7 @@ authors = ["Alex Crichton <alex@alexcrichton.com>"]
 license = "MIT/Apache-2.0"
 repository = "https://github.com/rust-lang/pkg-config-rs"
 documentation = "https://docs.rs/pkg-config"
+readme = "README.md"
 description = """
 A library to run the pkg-config system tool at build time in order to be used in
 Cargo build scripts.