Fix for issue #33. The problem was, functype was returning a weird
string, something like:

    signum :: [#<Contract:0x007f8c0607a398
    @args_contracts=[Contracts::Num],
    @ret_contract=#<Contracts::Or:0x007f8c0607a7f8 @vals=[-1, 0, 1]>,
    @args_validators=[#<Proc:0x007f8c0607a140@/Users/yonkeltron/.rvm/gems/ruby-2.1.0/gems/contracts-0.3/lib/contracts.rb:178
    (lambda)>],
    @ret_validator=#<Proc:0x007f8c0607a078@/Users/yonkeltron/.rvm/gems/ruby-2.1.0/gems/contracts-0.3/lib/contracts.rb:178
    (lambda)>, @method=#<UnboundMethod: Example#signum>,
    @klass=Example, @has_func_contracts=nil>]

Turns out there was a rendering change between ruby 1.8 and 1.9. Take
this script for example:

    a = [0]
    p "#{a}"

This prints `"0"` on ruby 1.8, and `"[0]"` on ruby 1.9.