switch to ubuntu trusty 14.04

[Fahad-Alsaidi]

This required for Adding CTL support #2284.

[Fahad-Alsaidi]

I need help to fix this:

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ERROR: TestImagePath.test_path

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Traceback (most recent call last):

  File "/home/travis/build/python-pillow/Pillow/Tests/test_imagepath.py", line 62, in test_path

    p = ImagePath.Path(tuple(arr.tostring()))

SystemError: new style getargs format but argument is not a tuple

[wiredfool]

Lets make this a little tighter -- either just 5.4.1 or 5.4.0 < v <5.4.1.

The default case should be that we have to reaffirm this skip for each pypy that fails, not that we never run these tests again.

[wiredfool]

The getargs thing is a real bug in the C layer, it's not an issue with changing the test. I'll have to track that one down.

[wiredfool]

Ok, I was wrong, that's the same underlying issue.

I've confirmed that there's a regression in pypy 5.4 and 5.6, where it worked in 5.3. There's a workaround in #2294.

[wiredfool]

Closed in favor of #2294

[hugovk]

Merged via PR #2294.