fixed typo: s/have store/store/

two verbs, only needed one
s/useful by/useful for/

"useful by" is not actually meaningful here. also added some text tweaks
for clarity.
s/it's/its/

very common grammatical error
missing "an"
footnote: where to find more

mention of bindings was a bit random without context
Merge pull request #441 from gilesbowkett/have_store

Cleanup/fixes for controller guides