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
regenerate AIFF+WAV wrapper using swig 2.0.11 (#54)
fix spelling typo
Merge branch 'aiff' into wav
(to resolve merge conflicts)

Conflicts:
	taglib-ruby.gemspec
fix require path in test file
Try to find opt-dir for Heroku buildpack (#28)

On Heroku when building the extension, the taglib files are not
available via an absolute path. Instead, they are in a path like this:

  /tmp/build_0d73acfd-3d71-471a-ad6d-bbd02f5d55d8/vendor/taglib/lib/libtag.so

There are however multiple environment variables, one of them:

  GEM_HOME=/tmp/build_0d73acfd-3d71-471a-ad6d-bbd02f5d55d8/vendor/bundle/ruby/2.0.0

From this, we can extract the vendor path and append taglib to get the
opt dir we need.

It's not very clean, but it feels a bit better than using relative paths
using "..".

Also, it's only tested with the following buildpack, which downloads the
taglib binaries from somewhere (ugh):

https://github.com/mrrad/heroku-buildpack-taglib
add c++ code to create/update tags in a WAV file

also add c++ code to dump tags from a WAV file
remove ruby code to create tags in a WAV file
Add gem version badge
Update links, prefer https
Fix compiler override heading to be under Installation
Merge pull request #58 from robinst/heroku

Try to find opt-dir for Heroku buildpack (#28)
re-enable test that was temporarily commented out
read picture file within picture test context
Merge pull request #57 from tchev/wav

Add support for WAV
Regenerate SWIG wrappers using swig 2.0.12

The only "real" change is that ASSOCIATE_FILESYSTEM_ENCODING was added
to aiff and wav as well. The reason they were not there before was that
they were branched before that change was made on master.
Update copyright year
Merge pull request #61 from robinst/swig_2.0.12

Regenerate SWIG wrappers using swig 2.0.12
Add missing test files to gemspec