Glob files should throw warning and skip document when it cannot read document

[martyganz]

Currently when inspector reads documents and we cannot read/parse the document the file loader will throw an error that the extension is not supported but it actually cannot parse the document.

[kamilkisiela]

Does #70 fix it?

[martyganz]

Nope, I put the TODO in there to show that we still need to do something there. Does not fix it though.