Verify that given type is a textblock in setBlockType
Verify that given type is a textblock in setBlockType

Issue #291

tzuhsiulin/prosemirror,salzhrani/prosemirror,kiejo/prosemirror,salzhrani/prosemirror,kiejo/prosemirror,adrianheine/prosemirror,salzhrani/prosemirror,adrianheine/prosemirror,tzuhsiulin/prosemirror,kiejo/prosemirror,tzuhsiulin/prosemirror,adrianheine/prosemirror