Django 1.8 support and bootstrap3-sass readiness

[frostbtn]

I've back ported template node walker from django-compressor, so django 1.8+ templating is supported in offline compilation (django and jinja2 engines).

bootstrap3-sass requires 8 as sass compiler' floating point preision; libsass default is 5, this leads to layout problems. I've pulled precision level to settings.py (if not specified, defaults to libsass' default).

I also needed for offline compilation to output .css to the same directory as with SASS_PROCESSOR_ENABLED, so added --use-processor-root switch.

[jrief]

Huh, this is a huge pull request, thank you very much
I think it will result into a version jump to 0.3.
I will merge it locally and test it in my environment.
My problem is, that due to external constraints, I'm force to use Django-1.7.

[jrief]

BTW: Have you seen the function get-setting() introduced in 0.2.5? Could we use that inside .scss files to change the precision, or must we set the precision globally while compiling?

[frostbtn]

@jrief, I seen and used custom functions with SASS_PROCESSOR_ENABLED. Yet we need to support this feature in offline compilation as well. I've updated pull request with this.

As for precision, no, as far as I know, talks on include precision changing inside sass are still fresh (sass/sass#1122), and this default 5 is source of... inconvenience... for many UI framework developers. At the moment precision is compiler param, so custom functions can't help here.

[jrief]

I have merged your pull request with some minor modifications.
Something I could not understand, is the reloading of template_source_loaders in compilescss.py line 121.

Anyway in my project (still using Django-1.7) it works.

Can you please retest everything and add a few lines to the Changelog section. This then will be released as 0.3.0.