Modularize turf dependencies

[wboykinm]

Modularize turf dependencies

[mapsam]

@wboykinm I believe that, since we are still not fully using browserify to build dropchop, you'll have to do a similar thing that @jczaplew did with topojson:

1. include a source file in lib that requires the necessary modules
2. and a browserify command in gulp that builds the script for dropchop before ...
3. loading into the js_vendor command

[wboykinm]

All set here.

[wboykinm]

@nickpeihl I'm (understandably) getting turf is not defined here when I run dropchop locally with only the modules installed (instead of the whole package).

The parent object turf seems to be required, but (many apologies) I can't find where it's defined in the codebase to replace it. Adding it back to the vendorJS array points to a nonexistent node module, so that doesn't work. Other things that don't work include:

• var result = turf-buffer.apply(null, params);
• var result = buffer.apply(null, params);
• var result = turfBuffer.apply(null, params);