Documentation

[sfsinger19103]

• Improve documentation including link to testing data repo, link to algorithm for curating bar charts
• Closes Delete vote_type_list function #552
• Removes some obsolete routines (e.g., top_counts())
• Rename some internal functions for clarity
• Removes old MANIFEST.in file
• hides all references to psycopg2 inside database module
• Adds constants (outlier_zscore_cutoff, max_rus_per_bar_chart, number_of_charts)