Add custom proto install to travis

.travis.yml

@@ -1,7 +1,11 @@
 language: rust
-dist: xenial
 before_install:
-  - sudo apt-get install -y protobuf-compiler
+  - curl -OL https://github.com/google/protobuf/releases/download/v3.4.0/protoc-3.4.0-linux-x86_64.zip
+  - unzip protoc-3.2.0-linux-x86_64.zip -d protoc3
+  - sudo mv protoc3/bin/* /usr/local/bin/
+  - sudo mv protoc3/include/* /usr/local/include/
+  - sudo chown $USER /usr/local/bin/protoc
+  - sudo chown -R $USER /usr/local/include/google
 script:
   - cargo build --verbose --all
   - cargo test --verbose --all