Update to 1.3

Upstream changes:
CHANGES IN formatR VERSION 1.3

NEW FEATURES

o `tidy_source()` can deal with multibyte characters that cannot represented
in the system native encoding now (on Windows)

o `usage()` works for functions obtained from `::` or `:::` now, e.g.
`usage(formatR::tidy_source)`

  CHANGES IN formatR VERSION 1.2

MAJOR CHANGES

  o the minimal required R version is 3.0.2 now

  CHANGES IN formatR VERSION 1.1

NEW FEATURES

  o added a new argument `output` to usage()

BUG FIXES

  o fixed yihui/knitr#918: when code is NULL, parse() will hang (with a question
  mark waiting for input)

(wen)