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.
Update TravisCI for Go 1.4 release.

Now that Go 1.4 has been released, this commit reverts the recent changes
which dealt with allowing TravisCI to work with go tip in between the Go
1.3 and Go 1.4 release cycle and updates the .travis.yml to invoke test
coverage tool from the new path in Go 1.4.