dir() doesn't list attributes added to an object using, e.g., from_fits_file()

[tmcclintock]

The function DataObject.from_fits_file() returns a cls(array) object containing data that was pulled out of a fits file. The columns should appear as attributes somewhere, but they are not listed when we run dir().

EXAMPLE:
In test_cluster.py in the setUp() function, we run:

self.cluster.members = GalaxyCatalog.from_fits_file(self.file_path + '/' + filename)

If we immediately write

print dir(self.cluster.members)

we see that 'z' doesn't appear on the list, even though on the very next line we see that 'z' is an attribute of members. This makes things difficult to debug because there is no easy way to find attributes spit out by fits files. I do not believe this is the intended behavior.

[erykoff]

You know, I never used the dir() command. Anyway, looking at the python documentation https://docs.python.org/2/library/functions.html#dir when you have custom __getattrribute__() you also need to set a custom __dir__(). So that needs to happen.