Add support for WAV

- add support for
  - TagLib::RIFF::WAV::File class
  - TagLib::RIFF::WAV::Properties class

- added swig code for TagLib::RIFF::WAV classes.
- added test code for reading/writing tags (ID3v2)
    to/from WAV files, including cover-arts.
- added a WAV-encoded audio file with ID3v2 tags for tests.
- added documentation.

- Note: support for RIFF-INFO tag is not included,
    TagLib 1.7 does not support this.
add test code for examples shown in the documentation

this is to ensure that examples actually work
(first run test code, then copy/paste to documentation)
add script to add/update tags in .wav test file
add test code for examples shown in the documentation

this is to ensure that examples actually work
(first run test code, then copy/paste to documentation)
Merge branch 'wav' into stable

Conflicts:
	taglib-ruby.gemspec