Updates to the old PyFITS FAQ to better serve as an 'astropy.io.fits' FAQ, as more people are starting out using Astropy.  Removed a few questions mostly related to installation that are already covered generally by the Astropy installation docs.
Also make some slight updates to the docs on warnings
Apparently the label 'warnings' was already taken (I think it shouldn't be but I'm not going to try to track it down right now).
Fix incorrect object reference
This enhances the test_path open to the TestRunner to allow the path to be any .py or .rst file (as before) *or* any directory which might contain tests (including doctests under docs/)
Expand documentation for fill_values

fixes #2080
[skip ci]
Fix typo [skip ci]
Merge pull request #2904 from larrybradley/typo

Fix typo [skip ci]
Merge pull request #2902 from hamogu/fix2080_2

Expand documentation for fill_values
fixing gzip import issue 2774
Code now import both astropy and system gzip

For clarity the astropy gzip is called _astropy_gzip
and the system gzip is called _system_gzip.

All gzip.x statements have been changed to use the
_astropy_gzip.

All isinstances statements check both
Allow format specificiers as Column format strings & deal with masked values.
Also refactored the string tests, and added regression test against formatting
of np.float32, etc.  Because masked values now are OK: [closes #1026]
creating global variable with the two GzipFile types
Added test for gzip file suggested by Erik Bray.
adding issue 2783 to the changelog for 0.4.2
Merge pull request #2783 abostroem/gzip_fix
Add several FAQs concerning performance
Add mention of the license to the readme
Merge pull request #2911 from eteq/add-astropy-license

Add mention of the license to the readme
Merge pull request #2886 from embray/testing/test-docs-only

test --test-path allows directories as well as files