Add 'readme' and 'keywords' to Cargo.toml. (#198)

Fixes #174.

Author: ahmedcharles

Cargo.toml

@@ -1,16 +1,17 @@
 [package]
-
 name = "error-chain"
 version = "0.10.1-pre" # remember to update html_root_url
 authors = [ "Brian Anderson <banderson@mozilla.com>",
             "Paul Colomiets <paul@colomiets.name>",
             "Colin Kiegel <kiegel@gmx.de>",
             "Yamakaky <yamakaky@yamaworld.fr>"]
 description = "Yet another error boilerplate library."
+keywords = ["error"]
 categories = ["rust-patterns"]
 
 documentation = "https://docs.rs/error-chain"
 repository = "https://github.com/brson/error-chain"
+readme = "README.md"
 
 license = "MIT/Apache-2.0"