https://nodejs.org/api/addons.html#addons_building specifies that "The module_name must match the filename of the final binary (excluding the .node suffix).". While the mismatch between `mapbox-gl-native` and `mapbox_gl_native` hasn't caused issues so far, we should play by the book.
For (hopefully) better performance than creating a new v8::Context to
wrap each callback while still avoiding leaking memory with v8::FunctionTemplate.
Adds a JavaScript shim in front of module.exports.Map to wrap the
req.respond API internally and preserve the public callback-passing
API, while still exporting the correct prototype.
