Add goveralls

.travis.yml

diff --git a/.travis.yml b/.travis.yml
index cdd30d2..83e84ad 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,3 +7,9 @@
     - 1.3
     - 1.4.1
     - tip
+before_install:
+  - go get github.com/axw/gocov/gocov
+  - go get github.com/mattn/goveralls
+  - if ! go get code.google.com/p/go.tools/cmd/cover; then go get golang.org/x/tools/cmd/cover; fi
+after_success:
+    - $HOME/gopath/bin/goveralls -service=travis-ci