Enable keep attrs

[jhamman]

Fixes#138

[shoyer]

The commit history here is getting a little messy. Could you make a commit which only adds the keep_attrs option to DataArray and Variable on top of master? Then, if we merge this in first, you can rebase #137 on top.

[jhamman]

Agreed that this is messy and my apologies for trying to do too many things at once. I'm more inclined to wait until we're done with #137 if that's ok. Then I think it should be simple enough to merge the master back here and clean up the commit history. If you don't think that will work, I will put together a clean commit off master.

[shoyer]

That's fine, we can deal with #137 first.

[jhamman]

I'm closing this since, as you mentioned above, its gotten messy. I'm cleaning it up now and will reopen when I've got my act in order.

[shoyer]

I've found GitHub doesn't handle rebases on master very well -- you end up with a lot of extra commits in your PR which makes it hard to review. So the cleanest thing to do may be to open a new PR.

[jhamman]

Exactly, see #141 for new PR.