notebook changes. This is are some seriously messy commits but the notebooks seem to demand this
Merge branch 'npdoty-master'. Notebook for showing top posters
replace process.py activity measure with more concise Pandas manipulations
fixing notebooks to use new Pandas-based processing. relates to #46 #22 and #47
moving Analyzing Mail Senders work by @npdoty into the Plot Activity notebook adapted to Pandas formulation, related to #46
fix in processing to check for Message-ID; new matricize function; iPython notebook does a simple Levenshtein example
library functions for handling Levenshtein matrix, and a second, more focused visualization
change formatting of matplotlib output