Add leaflet-d3 dependency cache (#13)

* Add leaflet-d3 dependencies cache
* The final solution will be to introduce `frontend-maven-plugin` in a separate change 
* Bump library version

Author: baldram

README.md

@@ -33,7 +33,7 @@ Add the dependency:
 	<dependency>
 	    <groupId>pl.itrack</groupId>
 	    <artifactId>gwt-leaflet-d3</artifactId>
-	    <version>0.3.0</version>
+	    <version>0.3.1</version>
 	</dependency>
 ```
 

docs/dependencies/build-dependencies.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+echo "-> Build dependencies"
+npm install
+
+echo "-> Copy built dependencies"
+rm -rf ./dist
+mkdir ./dist
+cp ./node_modules/@asymmetrik/leaflet-d3/dist/*.js ./dist
+rm -rf ./node_modules
+rm package-lock.json 
+#git add ./dist
+
+echo "Success!"