Added logic to send select output to a function that will create a frequency table
Added parsing code to recognize freq prepended to select command
Added shell for function to convert data, columns, and M_c into a frequency table
Broke out function that calculates value frequencies
Broke out a smaller function to return values, freqs, and probabilities from a single column
Frequency table works for one column. Need to expand to work for multiple columns.
Resolved merge conflicts from merging in dev branch
Updated bql_grammar to include hist pre-command
Updated parsing and util code so that hist select works with new parser
Hist works with infer, select, and simulate
Added parsing support for freq in addition to hist - decided to have frequency table in addition to histogram table
Renamed old histogram_ functions to freq_ functions
Corrected typos and added start of function to use numpy.histogram
Histogram table is working for select, simulate, and infer
Moved df_drop outside of summarize_table, because it's also used by freq_table and histogram_table
Histogram bin number is now determined by Sturges formula
Added tests for freq/hist
Merge branch 'dev' of https://github.com/mit-probabilistic-computing-project/BayesDB into dev