1.3.0
  - Windows: use libwebp from Rtools if found

1.2.0
  - Windows: update libs

1.1
  - Setting quality = NA in write_webp() now uses lossless encoding

1.0:
  - Windows / Mac: update to libwebp 1.0
  - Fix some rchk errors

0.4
  - Fix autobrew for OSX Mavericks

0.3
  - Windows: update libwebp to v0.6.0
  - Add symbol registration
  - Extract autobrew from configure
