Reorganizing material to put novice + intermediate at top level
Removing explicit 'level' keys from Markdown files
Modified build to generate Markdown files for IPython Notebooks in the source directories so that the Jekyll build will put all the files in the right places.  (Having a separate CACHED directory is cleaner, but then we have to move or patch files after the fact to make links resolve.)
Drafting a lesson on working with climate data as a wrap-up for novices
Starting to convert to notebook
Converting a bit more to notebook form
Markdown version of climate example
Markdown version of spatial intro
Converting climate data example to notebook form
Merge branch 'master' into worked-example
Polishing the data download example
Fixing bug in code example
1.  Merging fixes for missing image files from @r-gaia-cs.
2.  Putting IPython Notebook stuff in a separate Makefile so it won't inadvertently trigger when doing a regular site build.
    This ensures that people who *don't* have IPython installed,
    and don't want to re-create the Markdown files for notebooks,
    won't accidentally try to do it.
Avoiding confusing terminology
Moving Python climate data example into 'extras' directory
Adding image files produced from IPython Notebooks
Merge pull request #428 from gvwilson/splitting-makefile

Simplifying Makefile and adding documentation.
Merge pull request #431 from mkcor/improvements

Avoiding confusing terminology
Initial lesson about python string formatting using the format() method
Removed solutions