3.0.0 (stable)

This is the first stable release of sigc++-3.0, installable in
parallel with sigc++-2.0.
Changes compared to the latest unstable release:

* Fix tuple_transform_each() for libc++
  (Kjell Ahlstedt) Issue #25 (Jeff Trull)

Documentation:
* Remove some obsolete documentation
  (Kjell Ahlstedt)

Tests:
* Make test_track_obj.cc compile with clang++
  (Kjell Ahlstedt)
* Don't call static method via instance
  (Murray Cumming)