imdata tag should be ignored if included in input dataset

[Mike Timm]

If the tag:

<imdata totalCout=1>

is included in the input dataset arya outputs:

imdata = cobra.model.im.data(topMo, totalCount='1')

im.data is not a valid package.class. The im.data tag should be ignored/filtered on input.

[Paul Lesiak]

Resolved in the latest commit by checking the object key/tag and if it's "imdata", bypasses it. This fix is as far as I think we can go without making arya depend on cobra, before ensuring the input is valid, so for any other issues like this, we'll just have to ask people to make sure their input is properly formed