Adds limit = 0 as a valid parameter for queries (#1493)

* Remove results if limit = 0;

* Adds tests for limit=0 and count=1.

* Improves readability.

src/RestQuery.js

@@ -325,6 +325,10 @@ RestQuery.prototype.replaceDontSelect = function() {
 // Returns a promise for whether it was successful.
 // Populates this.response with an object that only has 'results'.
 RestQuery.prototype.runFind = function() {
+  if (this.findOptions.limit === 0) {
+    this.response = {results: []};
+    return Promise.resolve();
+  }
   return this.config.database.find(
     this.className, this.restWhere, this.findOptions).then((results) => {
     if (this.className === '_User') {