For issue #236

[weixuanfu]

[please review the contribution guidelines prior to submitting your pull request. go ahead and delete this line if you've already reviewed said guidelines.]

What does this PR do?

Make TPOT fail gracefully when all pipelines fail to evaluate (issue #236)

Where should the reviewer start?

From Line 307 in tpot.py

How should this PR be tested?

Run the codes with the data in the issue #233

Any background context you want to provide?

Just add a 'if' sentence to determine whether all pipelines are failed

What are the relevant issues?

The issue #236 links to the issue #233 and issue #234

Screenshots (if appropriate)

Questions:

• Do the docs need to be updated?
  No
• Does this PR add new (Python) dependencies?
  No

[coveralls]

Coverage decreased (-0.09%) to 89.699% when pulling 89c19ac on weixuanfu2016:weixuan-contribution into a381392 on rhiever:master.

[rhiever]

Thank you @weixuanfu2016!