Update version of Golang used to build

Author: jszwedko

circle.yml

@@ -1,12 +1,11 @@
 machine:
   environment:
     IMPORT_PATH: "github.com/$CIRCLE_PROJECT_USERNAME/$CIRCLE_PROJECT_REPONAME"
-    GO15VENDOREXPERIMENT: 1
     GOPATH: /home/ubuntu/.go_workspace
 dependencies:
   override:
   - sudo rm -rf /usr/local/go
-  - curl https://storage.googleapis.com/golang/go1.7.1.linux-amd64.tar.gz | sudo tar -C /usr/local -xz
+  - curl https://storage.googleapis.com/golang/go1.7.3.linux-amd64.tar.gz | sudo tar -C /usr/local -xz
 
   # Remove cached Go sources
   - rm -rf $HOME/.go_workspace