swc-windows-installer.py: Generalize msysGit download link

SWC's current setup instructions use both "Git for Windows" and "Git
Bash" [1].  They link to the Git for Windows installer [2] and not the
msysGit installer [3].  Since SWC has Make lessons [4], I think it
makes more sense to have students installing msysGit (which has Make
[5]) than to have them install Git for Windows (which does not have
Make [6]).

However, none of this matters for *this* Windows installer.  Because
this script works with both the full msysGit and the minimal Git for
Windows, I'm sticking to msysGit (the more generic project name), and
generalizing the suggested link to
http://code.google.com/p/msysgit/downloads/list.

[1]: https://github.com/swcarpentry/bc/blob/5c26313b0525e9d0b911d9558592a9e33cd03c1e/_includes/setup.html#L86
[2]: http://code.google.com/p/msysgit/downloads/list?q=full+installer+official+git
[3]: http://code.google.com/p/msysgit/downloads/list?q=installer+hack+on+git
[4]: https://github.com/swcarpentry/bc/tree/master/intermediate/make
[5]: https://github.com/msysgit/msysgit#the-build-environment
[6]: https://github.com/msysgit/msysgit#the-relationship-between-msysgit-and-git-for-windows
swc-windows-installer.py: Install the sqlite3 shell

On Thu, Apr 03, 2014 at 09:38:38AM -0700, Ethan White wrote:
> Some instructors like to teach `sqlite` from the command
> line. Therefore we should have the Windows installer handle
> downloading, installing and adding sqlite3 to the path.

The novice/sql lessons currently revolve around some IPython magic,
but even they use the SQLite shell to do the initial database setup
[1].  The SQLite shell has also seen a bit more developer time than
our one-off magic [2], so it's probably more robust ;).

I've installed this in it's own directory (rather than just dumping it
into ~/.swc/bin), because zip_install uses the existence of
${INSTALL_DIRECTORY} to decide whether or not the installation has
already happened.  create_nosetests_entry_point will have already
created ${BIN_DIR}, so we need to use a different target directory for
SQLite.  We could also flip the order and run install_sqlite first,
but that doesn't scale well if we install more packages in the future,
and it's easier to keep the installs separate and keep adding to the
path.

[1]: https://github.com/swcarpentry/bc/blob/1aa0799ac6a48e9815d50bf2f49171b9eb5bf6d4/novice/sql/README.txt#L8
[2]: https://github.com/swcarpentry/bc/blob/1aa0799ac6a48e9815d50bf2f49171b9eb5bf6d4/novice/sql/sqlitemagic.py
Merge branch 'python' into bc-namespaced-python

* python:
  swc-windows-installer.py: Install the sqlite3 shell
  swc-windows-installer.py: Generalize msysGit download link