Remove array dependencies from url helpers

The $parameters variable is being type casted to an array in the to() function of UrlGenerator so there isn't a need to require the parameter to be an array.

Signed-off-by: Dries Vints <dries.vints@gmail.com>
Update documentation for mixed parameters

Signed-off-by: Dries Vints <dries.vints@gmail.com>
Merge pull request #559 from driesvints/dv/remove-array-dependencies

Remove array dependencies from url helpers