Update readme with proposed new api
Shorten installation section.

People know how bundler works by now.
Don't need strong parameters

Since operations automatically filter the given parameters into the
(white)list of attributes they specify, we don't always need the
controller to do this whitelisting again. This cleans up the example
code a bit.
Remove section on callbacks

Since we decided to postpone support for them, we shouldn't keep it in
the README.
Add example showing how to use the context
Rewrite section on authorization to show examples
Write some words about contexts, and add example of how to use it in tests
Force a recent version of RSpec so we can use the spies feature
Move authorization and validation to #call
Merge pull request #29 from Factlink/feature/move-checks-to-call

Move validation and authorization checks to call
Swap out custom arguments code for Virtus
Lock Virtus at very specific version due to monkey patch
make sure virtus is loaded before patching
Move the stuff that Virtus does for us to spec/integration
Replace remove_const with stub_const
add newline
Remove support for finish_initialize
Merge pull request #28 from Factlink/feature/virtus

Use Virtus for attributes
Check that attributes either have a given value or a default
Add a Rails generator for 'pavlov:install'

This command adds a `app/backend` directory and sets up Rails'
autoloading for that path.