Rspec install

Atrodo, kad tas "be" matcheris nori true/false. Pats metodas "validate" grąžina stringą arba nilą. 
Prie tokio `expect(subject.validate({uploaded_file:file})).to be` gaunu:
````
Failure/Error: expect(subject.validate({uploaded_file:file})).to_not be
       expected "Unsupported file extension" to evaluate to false
````