Tidy up recipes.

Make names slightly more consistent.
Examples for authenticating and posting a form
Use IOException in Callback failure method.
Merge pull request #922 from square/jwilson_0611_more_recipes

Examples for authenticating and posting a form
Merge pull request #921 from square/jwilson_0611_tidy_examples

Tidy up recipes.
Merge pull request #923 from square/jw/failure-io

Use IOException in Callback failure method.