remove requirement that api auth requests be GET or POST

this is not necessary though we do still require that oauth exchange
requests use POST, per the spec
cleanup

oops
Merge pull request #90 from stormpath/fix-apiauth-methods

remove requirement that api auth requests be GET or POST
update readme and package.json
Merge pull request #91 from stormpath/release-0.5.2

Release 0.5.2

Fixes #89