Properly handle annotations in fenced code blocks

[rpaul-stripe]

This PR fixes issue #390 — annotations inside of fenced code blocks apply their attributes to the top-level document node. The expected behavior is for annotations inside of fenced code blocks to result in a validation error.

The logic inside of the parser sets the value of the inlineParent variable to the immediate parent when it detects that the current token has children. This behavior is mostly correct, because in markdown-it the only tokens that ever have a children array are "inline" tokens. The processing for fenced code blocks is, however, a special case — we modify the token and put the synthesized tokens for the parsed interior text content into the fence's children array. This inadvertently results in the fence's parent being treated as the inlineParent for the nodes nested inside of the fence.

To address this issue, I modified the parser logic so that it only sets the inlineParent variable when the current node type is explicitly "inline".

Closes #390