number with 0 fractional part should parse to an xsd:integer

The following JSON-LD
```json
{ "ex:value": 42.0 }
```
should result to the following triple
```turtle
[] <ex:value> "42"^^xsd:integer.
```
but PyLD produces this instead:
```turtle
[] <ex:value> "42e0"^^xsd:double.
```