Add test for the case where we try to read a file with an unhandled extension
Replace get_populated_generator with setUpClass
More refactoring for test_generators

- list comprehensions for distill_articles/pages
- distill articles only once
- pep8
Refactor pelican_open using contextmanager
Remove the reference to the PDF generation in the docs. Fix #1013
Merge pull request #1007 from saimn/refactor-tests

Refactor test_generators and pelican_open
fix py3 support for sourcecode directive

added sourcecode to the functional test so it's tested *somewhere*.
fixes #963
Merge pull request #1002 from russkel/sourcecodefix

fix py3 support for sourcecode directive
Support TAGS_* and AUTHORS_* by default.
Explicitly set locale when generating test output
Adds Rackspace Cloud Files support to quickstart and fabfile
Added more pygments options for code blocks
Merge pull request #1015 from karmadharma/morepygmentsoptions

Adding more options for pygments syntax highlighting
Refactor readers and remove MARKUP

Add a `Readers` class which contains a dict of file extensions / `Reader`
instances. This dict can be overwritten with a `READERS` settings, for instance
to avoid processing *.html files:

    READERS = {'html': None}

Or to add a custom reader for the `foo` extension:

    READERS = {'foo': FooReader}

This dict is no storing the Reader classes as it was done before with
`EXTENSIONS`. It stores the instances of the Reader classes to avoid instancing
for each file reading.
Disable asciidoc files for tests
Add a signal to give access to the dict of Reader classes.
Move the "find image with an empty alt" block in a function.
Add documentation for readers.
Merge pull request #974 from dbrgn/tags_authors_setting_fix

Tags/Authors Setting Fix
Merge pull request #1011 from saimn/readers

Refactor readers and remove MARKUP. Fixes #866