Add new maintenance branch format to Travis (#987)

Add new maintenance branch format to Travis (#987)

* Added new maintenance branch format to Travis

The maintenance branch format appeared to change from
`[version]-maintenance` to `[version].x` in the recent months, and
this broke Travis CI builds made to those branches. Because they
no longer meet the branch regex, the pull requests builds against
these branches were no longer being run.

This ads the regex for any branch which ends in `.x`, which should
catch the new pattern for maintenance branches.

* Use the branch regex from werkzeug

This is more specific to only catch version number branches.

* Sync with master

Apparently the build configuration for this branch is very old and doesn't match master at all.