tidyr 0.6.0

API changes

• drop_na() removes observations which have NA in the given variables. If no
  variables are given, all variables are considered (#194, @JanSchulz).
• extract_numeric() has been deprecated (#213).
• Renamed table4 and table5 to table4a and table4b to make their
  connection more clear. The key and value variables in table2 have
  been renamed to type and count.

Bug fixes and minor improvements

• expand(), crossing(), and nesting() now silently drop zero-length
  inputs.
• crossing_() and nesting_() are versions of crossing() and nesting()
  that take a list as input.
• full_seq() works correctly for dates and date/times.