This reverts commit fa77a5ac, reversing
changes made to 5843bc4d.

On Fri, Jan 23, 2015 at 04:30:14AM -0800, Matt Burke (GitHub Staff) wrote:
> The importer was supposed to be setting the HEAD ref.  There was a
> race condition that prevented it from doing so in some cases.  I
> just pushed out an update that should fix this issue.  Please let me
> know if it's still not working.

So the issue we were working around with #143 should be fixed now.

Add new CSS classes in preparation for merging CSS with main site

Telling people to change the default branch before cloning

Updating setup instructions to reflect use of GitHub Import.

Fixed link to go to old versions of git

1.  Modify README.md and other files to reflect use of GitHub Import.
2.  Modified URLs for shared files in `_include` files to get the right images and CSS.

This turned up #137: the CSS files for the workshop template, the main
website, and the lesson repository are all out of step and need to be
synchronized.  Once that is done, the URLs in the
`_includes/header.html` file should be updated

Clarifying docs and checking for missing end-of-YAML.

The code.google.com link from before went to a page with no versions of git for older Macs. I've linked to the sourceforge set of download links linked to from git-scm.com.

Improve python2 compatibility wrt unicode: use basestring instead of str

Add requirements.txt

Close #119.

Simplifying YAML header reading

1. Changing the way we load YAML header.
2. Modifying tests to reflect this.

Note that we no longer test for duplicated keys, because the YAML
module takes the last key seen rather than reporting an error.

Updated mac git instructions

Add language field to YAML header

Improve error message in `check.py`; remove redundant line in README.py

Add link for "below" installing ruby/github-pages, and disclaimer that these need to be installed, earlier in the document

The previous commit introducing check_blank_category() makes the check after
that for duplicate categories. The occurrence of multiple blank lines throws
two errors wuth that ordering: duplicate categories and presence of blank
lines. Testing for blank lines first allows for their removal, and avoids
reporting a confusing second error message from the same problem.

If the index.html header contains a blank line, check.py returns an error
indicating "superfluous categories". This message was unclear about the cause
of the error. This change reports the presence of blank lines in the header
specifically as an error.

Know the language that our instructors are using should be
important.