Parameter schemas don't use schema cache

[alexrjones]

Just started using this library and it's working great for us so far. However, I noticed when stepping through the library with a debugger that parameter validation (eg validating path parameters) appears to recompile the JSON schema for each validated parameter on every request (eg in parameters.ValidateSingleParameterSchema and parameters.ValidateParameterSchema).

#187 introduced a cache for schemas - unless there's a good reason not to that I'm not seeing, I think parameter validation should use this cache too. validator.warmSchemaCaches seems to pre-populate the caches already, even.