Wordsmith integration pages and fix various issues

This wordsmiths the integration pages and also fixes various issues like unclosed HTML tags, missing examples, spelling, grammar,  headings, etc.

**Note:** This does not fix the missing sections on how to add locale data to the pages — that'll be in another PR.
So we should probably following the standard title capitalization rules. Luckily there's a very handy tool that makes this easy for us: http://titlecapitalization.com/