Update from package template - all in one gigantic commit

Update to newer ez_setup.py

Add the current version of ah_bootstrap--for the tests themselves we will always copy over the latest version of ah_bootstrap (so that we can test ah_bootstrap itself), but there should still be a default copy of it in the package-template repo as well

Configure the package-template to use astropy_helpers.  By default includes astropy_helpers as a submodule. Yes, astropy_helpers is now a submodule of package_template which is a submodule of astropy_helpers

update the astropy_helpers version to include fix from c3f841b9e099f506a751b8a6971b15e7e3d6590a

Update the astropy_helpers version used in the package_template

Update the astropy_helpers version again; use the auto_use feature of ah_bootstrap.

Switch to using astropy_helpers for docs build.

Updated astropy_helpers version (included fix for Python 3)

Update the git submodule path to use http instead--hopefully this will work then on Travis

Updating to the actual astropy-helpers

Updated astropy-helpers to latest version

Fixing docs links in package test function

Updated astropy-helpers to latest version.

This version includes fixes for the coverage testing in affiliated packages.

Use wheels for travis testing

Care is taken to use a numpy wheel whose version matches the scipy/astropy wheels.

Previous commit messages:
Use development astropy for test --coverage
Install coverage when needed
Add cython to the travis build environment, controlled by an environmental variable
Also added a few more words of advice to the travis part of the README
Restore -w option to build_sphinx
Change URL for numpy-specific wheels and make scipy an optional install
Fix latest stable numpy version
Several tweaks to improve performance and reduce unnecessary tests
Remove debugging statements and cython install in egg_only

Don't override package data after it's been determined from
setup_package.py files

Include astropy_helpers in the affilated package's tarball.

removed setuptools_bootstrap.py as it doesn't exist any more in the new package-template

added ah_bootstrap and setup.cfg

Update astropy_helpers

Use MiniConda for affiliated packages

Make sure conda’s astropy is removed before pip installing the latest developer version

Added more comments to .travis.yml

Pin Numpy version

Don’t use --parallel with Python 3

More tidying up of .travis.yml file

Move astropy dev builds earlier in .travis.yml

Since they take longer, it is better to start them sooner for improved load balancing.

Import astropy_helpers from inside the docs/ directory

Fix a warning that "Could not determine version of package ccdproc" from
configuration system (since the __version__ member doesn't yet exist for
the package when the configuration file is copied).

More detail in example __init__.py

Add coveralls --rcfile option

Use the version module correctly in edit_on_github

Closes #55.

Added files to ignore in affiliated package coverage tests

Clarify purpose of cextern directory.