Travis: allow beta failure due to "ICE"

Ref: rust-lang/rust#47639

Author: sorpaas

.travis.yml

@@ -5,4 +5,6 @@ rust:
   - nightly
 matrix:
   allow_failures:
-    - rust: nightly
+    - rust:
+      - nightly
+      - beta

README.md

@@ -1,6 +1,6 @@
 # SECP256K1 Implementation in Pure Rust
 
-[![Build Status](https://travis-ci.org/sorpaas/libsecp256k1-rs.svg?branch=master)](https://travis-ci.org/sorpaas/libsecp256k1-rs)
+[![Build Status](https://travis-ci.org/ethereumproject/libsecp256k1-rs.svg?branch=master)](https://travis-ci.org/ethereumproject/libsecp256k1-rs)
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](./LICENSE)
 [![Cargo](https://img.shields.io/crates/v/libsecp256k1.svg)](https://crates.io/crates/libsecp256k1)
 [![Documentation](https://docs.rs/libsecp256k1/badge.svg)](https://docs.rs/libsecp256k1)