Update minimum version and test on it

.travis.yml

@@ -3,7 +3,7 @@ sudo: required
 rust:
 - nightly
 - beta
-- stable
+- 1.3.0
 addons:
   postgresql: 9.4
 before_script:

README.md

@@ -57,7 +57,7 @@ fn main() {
 ```
 
 ## Requirements
-* **Rust** - Rust-Postgres is developed against the 1.2 release of Rust
+* **Rust** - Rust-Postgres is developed against the 1.3 release of Rust
     available on http://www.rust-lang.org. It should also compile against more
     recent releases.