dtplyr 0.0.3

• Maintenance release for CRAN checks.

• inner_join(), left_join(), right_join(), and full_join(): new suffix
  argument which allows you to control what suffix duplicated variable names
  receive, as introduced in dplyr 0.5 (#40, @christophsax).

• Joins use extended merge.data.table() and the on argument, introduced in
  data.table 1.9.6. Avoids copy and allows joins by different keys (#20, #21,
  @christophsax).