Update dependencies, make the package work in Node.js 10-14

Also:
* Delete generated temporary files
* Stop using the deprecated constructor-based Buffer signature

Closes #6
Ref jquery/download.jqueryui.com#552

Author: mgol

.nvmrc

@@ -0,0 +1 @@
+10

lib/themeroller-image.js

@@ -57,7 +57,7 @@ function stream2Buffer( callback ) {
 
 		stdin.on( "end", function() {
 			var i = 0,
-				buffer = new Buffer( dataLen );
+				buffer = Buffer.alloc( dataLen );
 			if ( err.length ) {
 				return callback( new Error( err ) );
 			}
@@ -128,6 +128,9 @@ var generateIcon, generateImage, generateTexture,
 		task( callback );
 	}, concurrentQueues );
 
+// We'll `resume()` it once we know the ImageMagic version.
+imageQueue.pause();
+
 generateImage = function( params, callback ) {
 	if ( params.icon ) {
 		generateIcon( params.icon, callback );
@@ -347,6 +350,7 @@ async.series([
 			if ( !semver.valid( imVersion ) ) {
 				return callback( new Error( "Could not identify ImageMagick version.\n" + output ) );
 			}
+			imageQueue.resume();
 			callback();
 		}));
 	}