Upgrade dep to version 3.2

Upgrade dep to take advantage of bug fixes and performance improvements:
https://github.com/golang/dep/releases/tag/v0.3.2
https://github.com/golang/dep/releases/tag/v0.3.1

Versions 3.1 and later are no longer zipped:
golang/dep#957

Author: mattbostock

.travis.yml

@@ -11,9 +11,8 @@ before_install:
   - sudo apt-get -y -o Dpkg::Options::="--force-confnew" install docker-ce
 
 install:
-  - curl -sLo temp.zip https://github.com/golang/dep/releases/download/v0.3.0/dep-linux-amd64.zip
-  - unzip temp.zip
-  - rm temp.zip
+  - curl -sLo dep https://github.com/golang/dep/releases/download/v0.3.2/dep-linux-amd64
+  - chmod +x dep
   - cp dep $HOME/gopath/bin/
 
 script: