Added SST data to Lesson 3
Found more suitable data file (4D) for Lesson 3
Updated Lessons 3 and 4 to use NCEP GODAS multidimensional data file
Lecture notes completed for DA and Viz course, pending proof-reading and possible addition of new references
Merge branch 'master' of https://github.com/jonblower/python-viz-intro

Merge of content changed on the GitHub site