Bumped Travis CI to Go version 1.14.1.
Bumped Travis CI to Go version 1.14.1.

This commit bumps the Go version used on Travis CI (for testing and
builds) to Go 1.14.1.

Signed-off-by: Jacob Howard <f862f167b85d41b225785c70d70808bc7337c1fe@havoc.io>

havoc-io/mutagen,havoc-io/mutagen