chore: Try Ubuntu Trusty for Travis CI

[ntwb]

Currently Travis CI uses Ubuntu Precise 12.x, lets try Ubuntu Trusty 14.x to see if there is any performance benefit

cc @nylen

Related: #1808

[coveralls]

Coverage remained the same at 17.816% when pulling 6b802cb on try/trusty-travis into 4564ee0 on master.

[ntwb]

There doesn't seem to be much of a performance change 🤔

[ntwb]

Travis CI have just announced they'll be switching to Trusty by default

They'll start switching repos to Trusty July 18th

https://blog.travis-ci.com/2017-07-11-trusty-as-default-linux-is-coming

With the recent EOL of Ubuntu Precise, we are planning to begin setting the default distribution for builds to Ubuntu Trusty 14.04 on Tuesday, the 18th of July. Said another way, projects without an explicit dist YAML key in their .travis.yml file will be routed to Trusty instead of Precise. The tentative plan is to default 100% of configurations to dist: trusty by the end of August 2017.
...
As mentioned in the introduction, our tentative plan is to default 100% of incoming configurations to dist: trusty by the end of August 2017. Once this rollout is complete, our attention will turn to the retirement of container-based Ubuntu Precise. The tentative plan is to begin overwriting configurations that specify dist: precise to include sudo: required beginning in September 2017.

By the end of September 2017, we hope to have 100% of incoming configurations with dist: precise routed to the sudo-enabled infrastructure, and to retire the container-based infrastructure. We have no immediate plans to discontinue support for jobs that specify sudo: required and dist: precise, although we do not plan to update the images for these jobs any more.

As such we are going to require this PR regardless of performance changes.

An extra change for the PHP 5.2 job adding sudo: required is required, I'll add that momentarily

[ntwb]

FYI: sudo: required jobs take 20-50 seconds to spin up, see Travis CI docs here

Though thats the least of our problems, PHP 5.2 isn't available on sudo: required jobs 😱

[ntwb]

Per the Travis CI announcement post PHP 5.2 will not be available for testing come September 2017

The tentative plan is to begin overwriting configurations that specify dist: precise to include sudo: required beginning in September 2017

Once the force sudo: required change is implemented PHP 5.2 jobs will begin to fail as PHP 5.2 will no longer be available on Travis CI

See also travis-ci/travis-ci#8072: Trusty as default Linux is coming leaves no way to run PHP 5.2 jobs

[ntwb]

Also merged the same/similar change for WordPress Core just now:

https://core.trac.wordpress.org/changeset/41072

[nylen]

See also: https://blog.travis-ci.com/2017-07-11-trusty-as-default-linux-is-coming