relabel 'What is Fixity?' as 'Introduction' (#365)
relabel 'What is Fixity?' as 'Introduction' (#365)

* reimplement section title removal post rebase

* and remove another extraneous h2

* restore overall fixity section h2 and change subordinate h2 to h3

* whatever it takes

fcrepo/fcrepo-specification,fcrepo/fcrepo-specification