Fix route -> parent template matching

[BerkeleyTrue]

This commit also removes the need for underscore.string

[KyleAMathews]

Thanks!

[jlengstorf]

Hiya @BerkeleyTrue! 👋

This is definitely late, but on behalf of the entire Gatsby community, I wanted to say thank you for being here.

Gatsby is built by awesome people like you. Let us say “thanks” in two ways:

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