v0.4.0

- add dtools.filter() to work with either arrays or objects
- add dtools.filterObject(), filterKeys() and filterValues() to filter
  Objects by key + value, key or value, respectively
- tighten up dtools.unique()
- add dtools.uniqueCount() to count the number of unique values
- add dtools.common() to produce common value summaries
- add dtools.longest() and shortest()
- allow property alias Object inputs to summarize.properties()
csvstat.js rolls up CSV statistics, like csvkit's csvstat