Add support for Python 3.5

[maryokhin]

No description provided.

[maurizi]

You'll need to update the exclude configuration block below to remove the quotes around "2.6" to get the Travis CI builds to pass.

[maurizi]

@maryokhin Thanks for the PR!

Python 3 support has been desired by a number of folks for a while now, so I think we'll be happy to merge this if the Travis CI builds pass.

[coveralls]

Coverage remained the same at 100.0% when pulling b26da0a on Villoid:feature/python-3 into a5f7398 on azavea:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 2cb7c25 on Villoid:feature/python-3 into a5f7398 on azavea:master.

[maryokhin]

Yep, no problem @maurizi. Quick question though, Python 3.5 is failing of Django 1.7 because of this bug. Should I upgrade the test matrix to test on Django 1.7.5+ or just exclude the Django 1.7 + Python 3.5 row from the test matrix?

[maurizi]

Upgrading Django seems like the better option.

[coveralls]

Coverage remained the same at 100.0% when pulling 41e1e8a on Villoid:feature/python-3 into a5f7398 on azavea:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 3507a81 on Villoid:feature/python-3 into a5f7398 on azavea:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 9641e2c on Villoid:feature/python-3 into a5f7398 on azavea:master.

[jwalgran]

According to this chart, Django 1.7 is not supported under Python 3.5.

https://docs.djangoproject.com/en/1.7/faq/install/#what-python-version-can-i-use-with-django

We should exclude it from our matrix

matrix:
  exclude:
    - python: 3.5
      env: DJANGO=1.7

[coveralls]

Coverage remained the same at 100.0% when pulling 51e3fb7 on Villoid:feature/python-3 into a5f7398 on azavea:master.

[maryokhin]

A bit confused by all the string stuff in Python 2/3, but trying to figure it out. Can you mb explain what the sanitisation of strings and _safe_utf8_stringify does, @jwalgran?

[maurizi]

@maryokhin As noted on the Python website csv.DictWriter on Python 2 does not support unicode. So the purpose of _safe_utf8_stringify is to ensure that all unicode string content gets encoded as UTF-8 before being added to the CSV.

This may not be necessary on Python 3, as the docs do not have the same note about not supporting unicode that they do on the Python 2 version.

(Though obviously we'd like to continue supporting Python 2.7).