Error on 'npm install' - Unexpected key 'output' found

[gavinr]

When I run npm install in this repository, I get an error on the build portion:

> [email protected] build C:\.....\esri-leaflet-heatmap
> rollup -c profiles/debug.js & rollup -c profiles/production.js

Unexpected key 'output' found, expected one of: banner, dest, entry, exports, external, footer, format, globals, indent, intro, moduleId, moduleName, onwarn, outro, plugins, sourceMap
Error: Unexpected key 'output' found, expected one of: banner, dest, entry, exports, external, footer, format, globals, indent, intro, moduleId, moduleName, onwarn, outro, plugins, sourceMap
    at validateKeys (C:\.....\esri-leaflet-heatmap\node_modules\rollup\www\ROLLUP\rollup\src\utils\validateKeys.js:12:11)
    at Object.rollup (C:\.....\esri-leaflet-heatmap\node_modules\rollup\www\ROLLUP\rollup\src\rollup.js:39:16)
    at bundle (C:\.....\esri-leaflet-heatmap\node_modules\rollup\bin\runRollup.js:136:16)
    at execute (C:\.....\esri-leaflet-heatmap\node_modules\rollup\bin\runRollup.js:125:3)
    at C:\.....\esri-leaflet-heatmap\node_modules\rollup\bin\runRollup.js:69:4
    at tryCatch (C:\.....\esri-leaflet-heatmap\node_modules\rollup\www\ROLLUP\rollup\node_modules\es6-promise\lib\es6-promise\-internal.js:185:12)
    at invokeCallback (C:\.....\esri-leaflet-heatmap\node_modules\rollup\www\ROLLUP\rollup\node_modules\es6-promise\lib\es6-promise\-internal.js:197:13)
    at publish (C:\.....\esri-leaflet-heatmap\node_modules\rollup\www\ROLLUP\rollup\node_modules\es6-promise\lib\es6-promise\-internal.js:168:7)
    at flush (C:\.....\esri-leaflet-heatmap\node_modules\rollup\www\ROLLUP\rollup\node_modules\es6-promise\lib\es6-promise\asap.js:87:5)
    at process._tickCallback (internal/process/next_tick.js:61:11)
Type rollup --help for help, or visit https://github.com/rollup/rollup/wiki

Per jgravois:

the error is caused by the fact that this plugin imports a base rollup.config from Esri-leaflet, which was upgraded [....] quite awhile ago.

So I think we should update our Rollup dependency in this repo to match esri-leaflet's (v0.56.5 as of this writing) (and any applicable related rollup plugins, etc)

[gavinr]

Fixed in #25