Location and entry maps

used MapBox Api to generate map on location show page.  
--map displays marker for each entry near the map center.
--javascript is in the html file.  I was having trouble getting the ruby variables to work in a seperate js.erb file.  Help would be appreciated.
Ah, seeing this line and the `borders` method it became a bit clearer.

What about instead of calling `borders` ahead of time, we construct a `CoordinateArea` in another method and use that here.

For example

```ruby
entry.in_geo_area_nsew(coordinate_area)

def coordiante_area
  # ... do stuff
end
```