Refactor `HeaderNode#find_parent`
Refactor `HeaderNode#find_parent`

Now the instance variable assignment is all contained within
`#initialize`, and the `children.push` behavior is more explicit.

jirutka/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,mmkassem/gitlabhq,axilleas/gitlabhq,iiet/iiet-git,jirutka/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,dreampet/gitlab,dreampet/gitlab,stoplightio/gitlabhq,mmkassem/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,dreampet/gitlab,jirutka/gitlabhq