version 1.4 violates semantic versioning

[ScanMountGoat]

There are a number of compile errors in my gltf exporting code since some of the field types changed from u32 to USize64. I'm able to resolve this for now by fixing the version for both the gltf and gltf-json crate in the Cargo.toml.

[kpreid]

See #385 for existing discussion.