The REST doesn't prevent body inclusion with DELETE request but it is better to use query string as it is most standarized (unless you need the data to be encrypted)
I got it to work with angular 2 by doing following:
let options:any = {}
option.header = new Headers({
'header_name':'value'
});
options.search = new URLSearchParams();
options.search.set("query_string_key", "query_string_value");
this.http.delete("/your/url", options).subscribe(...)