Update TravisCI to work with go tip.

This commit modifies the .travis.yml to invoke a new script which has also
been added that gets the test coverage tool from the new path needed by go
tip.

.travis.yml

@@ -4,7 +4,7 @@ go:
   - tip
 install:
   - go get -d -t -v ./...
-  - go get -v code.google.com/p/go.tools/cmd/cover
+  - ./get_ci_cover.sh
 script:
   - go test -v -covermode=count -coverprofile=profile.cov
 after_success:

get_ci_cover.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env sh
+
+set -x
+if [ "$TRAVIS_GO_VERSION" = "tip" ]; then
+	go get -v golang.org/x/tools/cmd/cover
+else
+	go get -v code.google.com/p/go.tools/cmd/cover
+fi