Map json schema integer to go type int64
Map json schema integer to go type int64

Spec here: http://json-schema.org/latest/json-schema-validation.html#rfc.section.6.25
says integer 'matches any number with a zero fractional part' - so int64 is safer to
use than int, since it potentially covers a larger range of values if on a < 64 bit
environment. Another option would have been https://golang.org/pkg/math/big/#Int but
let's hold off implementing that until we're sure we need it, and it could break a
lot of existing code.

taskcluster/jsonschema2go,petemoore/jsonschema2go