added magrittr, minor edits to body of intro, rewrote questions, and edits to methods section 1st half
edited intro a little bit, and rewrote metabolic capacity section.
restruct methods, moving pianka up and filling in some more info.  also this commit includes some testy code for metabolic pianka approach.  Figure caption edits too.
romero citation
grammatical errors and changed DURATION
rewrote matrix_to_df()
removed plyr, and rewrote predators
moved pianka, paired_predator_pianka and matrix_to_df to R.scripts/FUNCTIONS_pred_div.R
added ... to function to allow for evaluation, an easy way to remove the Taxa variable.  (necessary to replace metabolic distance calculation with the new paired pianka predator fn
comments from DS on first paragraph.  Major rewrites of code, too.
minor edits to Intro, methods
edits to methods
DS comments to methods section
minor edits to the end of methods section
minor in-text edits to results section: experiment
take out some troublesome comments
caption of Fig 2
nice themes for graphs.  nonlinear coding section, too.
temporarily rm discussion
switched to using `do`