Update README.md

Extract "Development" into a separate file, to make the readme shorter. Affects beta.webcomponents.org listing significantly.

README.md

@@ -42,86 +42,7 @@ We encourage you to read the [contribution instructions by GitHub](https://guide
 
 ## Development
 
-Each element has it's own GitHub repository, where development is done. The vaadin-core-element project is just a top-level bundle without actual production code.
-
-Familiarize yourself with the code and try to follow the same syntax conventions to make it easier for us to accept your pull requests.
-
-The following instructions are common for all Vaadin core elements. **Replace `vaadin-combo-box` with any other element in the following examples**. Check the element readmes for any special development notes.
-
-### Getting the code
-
-1. Clone the element project from GitHub:
-
-  ```shell
-  $ git clone https://github.com/vaadin/vaadin-combo-box.git
-  ```
-
-2. Install [Node](https://nodejs.org/en/download/). It comes bundled with [npm](https://npmjs.com), which is needed to install other tooling.
-
-3. Install [Bower](http://bower.io) using [npm](https://npmjs.com):
-
-  ```shell
-  $ npm install -g bower
-  ```
-
-  > If you encounter permission issues when running `npm` see the article about [fixing npm permissions](https://docs.npmjs.com/getting-started/fixing-npm-permissions) on npmjs.com
-
-4. Use Bower to install the dependencies of the element:
-
-  ```shell
-  $ cd vaadin-combo-box
-  $ bower install
-  ```
-
-### Running demos
-
-1. Install [polyserve](https://github.com/PolymerLabs/polyserve) using [npm](https://npmjs.com):
-
-  ```shell
-  $ npm install -g polyserve
-  ```
-
-2. Start a local server in the project root directory:
-
-  ```shell
-  $ cd vaadin-combo-box
-  $ polyserve
-  ```
-
-3. Open the following URLs in your browser:
-  - Demo: http://localhost:8080/components/vaadin-combo-box/demo/
-  - Generated API documentation:  http://localhost:8080/components/vaadin-combo-box/
-
-### Running tests
-
-Install [Web Component Tester](https://github.com/Polymer/web-component-tester) using [npm](https://npmjs.com):
-```shell
-$ npm install -g web-component-tester
-```
-
-Tests can be run with the `wct` task from the element directory:
-
-```shell
-$ cd vaadin-combo-box
-$ wct
-```
-
-You can also run and debug the tests manually:
-```shell
-$ cd vaadin-combo-box
-$ polyserve
-```
-- Open http://localhost:8080/components/vaadin-combo-box/test/ in your browser.
-
-You should include new tests in your pull requests if you add features to the elements or if you are fixing a bug.
-
-### Documentation
-
-We follow the same [style guide](http://polymerelements.github.io/style-guide/) as Polymer.
-
-### Contributor License Agreement
-
-When you send a pull request to any of our repositories, you get an automated comment response about the CLA. It will notify you if you haven’t signed the CLA yet, and in that case instructions how to do it. You need to do this once per earch repository. Before we can accept any of your code contributions, you need to sign the CLA.
+If you want to develop the elements yourself see the [development instructions](DEVELOPMENT.md) that apply to all Vaadin elements.
 
 ## License