Add regression tests for https://github.com/spacetelescope/PyFITS/issues/25

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2226 ed100bfc-0583-0410-97f2-c26b58777a21
Added a ._data_replaced attribute on HDUs.  This is set to True if a data object other than the original data object loaded from a file is assigned to the HDU's .data attribute.  That way when writing updates to the file we know to write the new data rather than just flush the mmap of the old data.  This required a bit of refactoring in the _TableBaseHDU class to even support modifying the .data attribute in the first place--this is a feature that was never left out intentionally, it was just ommitted through carelessness and, I guess, not enough people asking to add it.  This isn't fully working yet though...

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2227 ed100bfc-0583-0410-97f2-c26b58777a21
Update the lazyproperty decorator so that custom setters can override the input value.  This is required for the _ImageBaseHDU and _TableBaseHDU data setters to really work in such a way that input values can be converted to the correct types.

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2228 ed100bfc-0583-0410-97f2-c26b58777a21