Added context for definition of a 'map' - computer maps have a short history.
Fix typo: unnecessary capitalization
Clarified and expanded shapefile explanation.
Topology is not always about 'touching'
Drawbacks of GeoJSON
Added 'deforestation' to what infra-red is used to map.
Merge branch 'gh-pages' into mizmay-gh-pages

Conflicts:
	README.md
Merge mizmay branch, update contributors.
Merge branch 'gh-pages' of github.com:tmcw/mapschool into gh-pages