Bump version to 4.0.0-alpha.6

Author: ramosbugs

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "oauth2"
 authors = ["Alex Crichton <alex@alexcrichton.com>", "Florin Lipan <florinlipan@gmail.com>", "David A. Ramos <ramos@cs.stanford.edu>"]
-version = "4.0.0-alpha.5"
+version = "4.0.0-alpha.6"
 license = "MIT/Apache-2.0"
 description = "An extensible, strongly-typed implementation of OAuth2"
 repository = "https://github.com/ramosbugs/oauth2-rs"