Add documentation

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
En-dash

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
Update rescue_from docs to be more realistic

We automatically rescue from Crepe::Params-based exceptions, so no need
to suggest them in the docs.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>
Improve documentation for Crepe::Endpoint#head

The `head` method also takes an undocumented options hash that maps to
HTTP headers. Document this to make it more discoverable.

Signed-off-by: David Celis <me@davidcel.is>
Consistent documentation whitespace

Signed-off-by: David Celis <me@davidcel.is>