Central / automatic read function

[ssomnath]

We need a simple read() function that can figure out which Reader to use when the user does not specify a specific Reader object. For this to be a reality, we need every Reader class to implement the can_read() function. In most cases, this will be trivial, all one would need to do is call __super__ and provide the file extension that this Reader handles.

I have already written a version of this in pycroscopy here. We just need to copy the contents and update some links.

[ssomnath]

This function should simply call upon the top-level modules and ask them for a list of available Reader classes. Alternatively, one could simply go over all and find out which of the objects are Reader classes. The main point is that this function should not need to know the Reader classes individually but just know that there may be many that this function will need to iterate over.