Django-ddp

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* Include ROOT_URL_PATH_PREFIX in ROOT_URL when serving Meteor build
files.

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* Use HTTPS for DDP URL if settings.SECURE_SSL_REDIRECT is set.

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* Added support for django.contrib.postres.fields.ArrayField
serialization.

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* Added Django 1.8 compatibility. The current implementation has a
hackish (but functional) implementation to use PostgreSQL's
`array_agg` function. Pull requests are welcome.
* Retained compatibility with Django 1.7, though we still depend on the
`dbarray` package for this even though not strictly required with
Django 1.8. Once again, pull requests are welcome.

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* Add missing dependency on `pybars3` used to render boilerplate HTML
template when serving Meteor application files.

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* Add `dddp.server` Django app to serve Meteor application files.
* Show input params after traceback if exception occurs in API methods.
* Small pylint cleanups.