Drop 7.10 from Travis CI.
Drop 7.10 from Travis CI.

We temporarily added 7.10 back for an important security fix. This
removes it from the automated build/test and eventually we will remove
7.10 again

chorrell/docker-node,nodejs/docker-node,joyent/docker-node,nodejs/docker-node,chorrell/docker-node,pesho/docker-node