Fix for issue 387

[ikurovsky]

Motivation:
OpenAPI v2 supports setting default values for array parameters, but current v1 parser implementation fails to read such document as it always assumes the default value to be string.

Modification:
In case if parameter type is set to "array" then parse the default value as array.

Limitations:
The fix only allows parser to read such documents without errors while internally the default value is still represented as string. Changing that would require update of a much wider scope as it includes changes in both swagger-parser and swagger-models.

Fixes #387.

[gracekarina]

thanks @ikurovsky