test failures with leaflet 1.1.0

[jgravois]

https://travis-ci.org/Esri/esri-leaflet/builds/243458201

we're seeing a handful of different failures, but they all result from FeatureLayer.createFeatures() not being called. manual testing confirms they are false positives, but i haven't been able to figure out why the spies aren't being triggered.

typically rogue errors like this are caused by the fact that the actual requests don't look enough like the urls sinon.fakeServer is poised to send responses for.

with this in mind, i tried substituting an overly generic regex, but found no joy.

server.respondWith('GET', new RegExp(/http:\/\/gis.example.com\/mock\/arcgis\/rest\/services\/MockService\/MockFeatureServer\/0\/query\?.+/), JSON.stringify({
    fields: fields,
    features: [feature1, feature2],
    objectIdFieldName: 'OBJECTID'
}));