Implement conversion that works in a simple case
Overwrite default xbins values
Include support for geom_bar and for non-numeric data
Add basic tests for histograms
Skip confusing step in retrieving x dimension
Default to autobinx True when binwidth not available (non-numeric data)
Do not force default geom_bar into histogram (yet)
Fix condition
Support multiple traces for histogram type in the future
Merge pull request #50 from ropensci/marianne-histogram

Conversion for geom_histogram