ExpectsXXX breaks the chain in ide.

[alekc]

Following code (taken from example)

$response = \Httpful\Request::get($uri)
    ->expectsJson()
    ->sendIt();

will invoke an error with "method undefined" in ide such phpstorm with result of not being able to use intellisense for next chained methods.

The reason for this is the usage of magic method for expectsXXX. I would suggest to add explicit methods for standard mime types, it should be slightly faster as well.