Add credit statement in docs.
Remove unnecessary virtual keywords.
Add transmission accessors test.
Add transmission interface class and test.
Remove dependency from manifest.
Add pthread dependency to tests.

After moving from Ubuntu 10.04 to 12.04 these dependencies need to be explicitly
stated in my dev machine. This should be looked upon in greater detail, as such
dependecies should be taken care of by rosbuild.
Use \name commands in documentation.
Remove pure virtual method.