Correct the allowed MPL licenses in licenseck.
Remove a glob import from tidy.py.
Remove unused code from tidy.py.
Stop using fileinput in tidy.py.

The code is expressed much more clearly with a loop over the files instead.
Fix PEP8 violations in tidy.py.
Test for trailing spaces in tidy.py.
Test for missing newlines at end of file in tidy.py.
Test for tabs in tidy.py.
Test for carriage returns in tidy.py.
Run tidy.py on Travis.
Merge pull request #2806 from Ms2ger/tidy

Improve and extend tidy.py, and run it on Travis.