.marker(): support multiple ways to specify the location data

currently, it's required to be an array of arrays: 

```
.marker([[-122, 37], [-87, 41]])
```

we were thinking it would be nice to also support just one array if you only have one marker:

```
.marker([-122, 37])
```

and maybe also an object or array of objects: 

```
.marker({long: -122, lat: 37})
.marker([{long: -122, lat: 37}])
```
