Fixes #168

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2130 ed100bfc-0583-0410-97f2-c26b58777a21
This should resolve #177 where it was determined that the best course of action would be to document the use case of manually closing mmaps.  The other suggestion, that there be a brief explanation of mmap, was already there as it turns out (though it needed a mention of the fact that memmap=True is now the default).

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2131 ed100bfc-0583-0410-97f2-c26b58777a21
Should fix #218

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2134 ed100bfc-0583-0410-97f2-c26b58777a21
Fixes spacetelescope/PyFITS#5

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2142 ed100bfc-0583-0410-97f2-c26b58777a21
For some reason the test_missing_tnull test just out of nowhere started erroring during teardown on Python 3 *only*.  I didn't change anything related to that (just added a new test) and this started.  As far as I can tell there is nothing actually preventing full garbage collection or all files being closed.  I think I've just hit some corner case that puts the garbage collector in a state where it doesn't *quite* close the mmap in time.  Let's just give the teardown a few attempts to remove the files and leave it at that.

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2143 ed100bfc-0583-0410-97f2-c26b58777a21
Fixes spacetelescope/PyFITS#6; although the specifications of the HIERARCH convention don't say anything about leading whitespace, CFITSIO's behavior is to strip it, and that is probably the expected behavior by most people.

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2152 ed100bfc-0583-0410-97f2-c26b58777a21