Don't pin django-braces and six versions

These two pinned dependencies make the package uncompatible with other (or at least some of my corporate project)

I just accepted latest versions.
Created a setting for the default value for approval prompt.
Shouldn't have committed this.
Merge pull request #108 from aaronromeo/approval-prompt-from-settings

Created a setting for the default value for approval prompt.
Merge pull request #107 from noirbizarre/patch-1

Don't pin django-braces and six versions
added tests spotting  known vulnerabilities
fixed settings documentation
added docs for approval_prompt parameter, fixes #92
removed unused docs module
minor adjustments and warnings suppression
fixed docstrings formatting
cleanup + docs for application views
moved out application views docs
applications views docs, fixes #44
changelog and readme updated
bumped version
added item to changelog