Add crate doc root

https://github.com/brson/rust-api-guidelines#c-html-root

Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 
 name = "lmdb"
+# NB: When modifying, also modify html_root_url in lib.rs
 version = "0.6.0"
 authors = ["Dan Burkert <dan@danburkert.com>"]
 license = "Apache-2.0"

lmdb-sys/Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 
 name = "lmdb-sys"
+# NB: When modifying, also modify html_root_url in lib.rs
 version = "0.6.0"
 authors = ["Dan Burkert <dan@danburkert.com>"]
 license = "Apache-2.0"

lmdb-sys/src/lib.rs

@@ -1,4 +1,6 @@
 #![allow(non_camel_case_types)]
+#![deny(warnings)]
+#![doc(html_root_url = "https://docs.rs/lmdb-sys/0.6.0")]
 
 extern crate libc;
 

src/lib.rs

@@ -2,6 +2,8 @@
 //! [Symas Lightning Memory-Mapped Database (LMDB)](http://symas.com/mdb/).
 
 #![cfg_attr(test, feature(test))]
+#![deny(warnings)]
+#![doc(html_root_url = "https://docs.rs/lmdb/0.6.0")]
 
 extern crate libc;
 extern crate lmdb_sys as ffi;