swc-windows-installer.py: Set default logging level to INFO

And add the other levels as --verbose choices, even though we
currently only use LOG.info and LOG.debug.  Many *nix commands are
silent by default and have options for increasing the verbosity, but
Ethan points out that we should probably default to the setting that
makes the most sense for new users.
swc-windows-installer.py: Add missing space to 'c:\ProgramFiles'

This is the default for when ProgramFiles isn't set.  Windows
operating systems should always have that environment variable set, so
the default is probably only useful when you're testing the script on
a non-Windows system.
swc-windows-installer.py: Search ProgramW6432 and ProgramFiles(x86)

It turns out that the 'ProgramFiles' environment variable is set
differently depending on the architecture of process in question.  To
always get the 32-bit x86 version, you should use 'ProgramFiles(x86)'
[1].  To always get the 64-bit amd64 version, you should use
'ProgramW6432' [2].

To be safe, and support both 32- and 64-bit Windows installs, just
search everything that could be relevant.  Prefer 64-bit locations
(when we have any).

[1]: http://technet.microsoft.com/en-us/library/cc749104%28v=ws.10%29.aspx
     Recognized Environment Variables
     ...
     CSIDL_PROGRAM_FILES  Version 5.0. The Program Files folder.
                          A typical path is C:\Program Files.
     ...
     PROGRAMFILES         Same as CSIDL_PROGRAM_FILES.
     PROGRAMFILES(X86)    Refers to the C:\Program Files (x86) folder on
                          64-bit systems.

[2]: http://msdn.microsoft.com/en-us/library/windows/desktop/aa384274%28v=vs.85%29.aspx#Environment_Variables
     WOW64 Implementation Details
     ...
     64-bit process:
        ProgramFiles=%ProgramFiles%
        ProgramW6432=%ProgramFiles%
     32-bit process:
        ProgramFiles=%ProgramFiles(x86)%
        ProgramW6432=%ProgramFiles%

     The ProgramW6432 and CommonProgramW6432 environment variables
     were added starting with Windows 7 and Windows Server 2008 R2.
swc-windows-installer.py: Add --version and start with 0.1

Since we're decoupling these scripts (and any installers derived from
them) from the per-workshop repository, it's good to have an easy way
for folks to see which version they're dealing with.
Merge branch 'python' for release 0.1
README.md: Link to GitHub releases for the most-recent compiled version

This way we don't need to remember to push to
files.software-carpentry.org.  The linked page has the message from
the latest release and a link to the exectuable, when it used to be
just the exectuable.  A quick search didn't turn up a way to link
directly to the latest binary.  I'm not particularly worried about the
additional click though, and folks working up installation
instructions for a given workshop should probably be linking to an
explicit version anyway.
README.md: Mention that R should be installed before running our installer

This came up in response to the v0.1 release announcement on
discuss@lists.software-carpentry.org [1].

I've also added a link to Python (and used it where we mention Python)
to match the existing link to R.

[1]: http://lists.software-carpentry.org/pipermail/discuss_lists.software-carpentry.org/2014-August/001932.html

Reported-by: John Blischak <jdblischak@uchicago.edu>
Merge pull request #15 from wking/r-instructions

README.md: Mention that R should be installed before running our installer
Merge pull request #14 from wking/latest-release

README.md: Link to GitHub releases for the most-recent compiled version