WIP: Switch over to using our own deprecation warning so that it will be more visible by users by default.  Currently this breaks many tests or at least causes a lot of extra output in the tests since there are tests of deprecated code that are causing this warning to be raised.

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2458 ed100bfc-0583-0410-97f2-c26b58777a21
Add a  function so that they can be turned off easily.

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2459 ed100bfc-0583-0410-97f2-c26b58777a21
Improve ignore_warnings so it can also be used as a method decorator.  Squelch deprecation warnings on various tests--for now I would rather leave these tests as-is, using the deprecated methods.  They are mostly older tests, and there is value in testing the deprecated intefaces so long as they're still kept around.

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2460 ed100bfc-0583-0410-97f2-c26b58777a21
Add a mention in the changelog of the deprecation warnings changes

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2461 ed100bfc-0583-0410-97f2-c26b58777a21