Drop support for Django <1.8 LTS

[mgrdcm]

This will be a breaking change for the purposes of semantic versioning, so we'll want to hold off until we're going to do a 1.0.0 release.

Django 1.8 is the oldest version of Django currently supported by the Django Project, and will be supported until April 2018.

This PR also drops support for Python 2.6.

Everyone: Let me know if I missed anything. I could move this to a django-import-export feature branch if we don't want to merge this right away.

[coveralls]

Coverage increased (+0.3%) to 90.876% when pulling 046d772 on mgrdcm:require-django-1-8 into 70b29bf on django-import-export:master.

[manelclos]

I agree with holding until 1.0.0

[bmihelac]

Can we create branch '0.6.x' from current master and merge this changes on master? Next release would then be 1.0.0.

[coveralls]

Coverage increased (+0.3%) to 91.539% when pulling 87afec4 on mgrdcm:require-django-1-8 into 318208c on django-import-export:master.

[mgrdcm]

@bmihelac Good idea! Though if <1.0.0 is going into bugfix/maintenance mode, I'd think we'd want the 0.6.x branch to based off of tag 0.6.0 rather than the current master branch, as master contains a bunch of unrelated changes we probably want to save for 1.0.0 now.

[bmihelac]

@mgrdcm or we can release 0.6.1 now and base 0.6.x on 0.6.1 tag

[mgrdcm]

@bmihelac Agreed! There's not a ton since 0.6.0 though. I have no opinion either way.

[bmihelac]

I think we are ready for 1.0. If there is no other suggestion:

• I will create branch 0.7.x (for any security or other important fix needed for older Django versions)
• merge this PR
• Release 1.0

@mgrdcm, @thauk-copperleaf, @manelclos did I forgot anything?

[manelclos]

Django 1.8 is supported "Until at least April 2018" (https://www.djangoproject.com/download/). LGTM otherwise.

[mgrdcm]

Hey @manelclos and @bmihelac! Sorry I've been distracted with other things. I just fixed the merge conflict on this.

[bmihelac]

No problem @mgrdcm and thanks!

I'll go with #685 (comment) asap.

[bmihelac]

Merged in e6d9be7, thanks!

[gabn88]

Just curious, will it also support Django 2.0 now?