Add a 'Quick development Setup' section to ease first contact with th…

…e repo.

Even if the information here are duplicate from http://docs.datadoghq.com/guides/integration_sdk/, this was requested by support to help bootstrap development.

README.md

@@ -4,6 +4,29 @@
 
 This repository contains the Agent Integrations that Datadog officially develops and supports. To add a new integration, please see the [Integrations Extras](https://github.com/DataDog/integrations-extras) repository and the [accompanying documentation](http://docs.datadoghq.com/guides/integration_sdk/).
 
+
+# Quick development Setup
+
+To get started developing with the integrations-core repo you will need: `gem` and `python`.
+
+We’ve written a gem and a set of scripts to help you get set up, ease development, and provide testing. To begin:
+
+- Run `gem install bundler`
+- Run `bundle install`
+
+Once the required Ruby gems have been installed by Bundler, you can easily create a Python environment:
+
+- Run `rake setup_env`. This will install a Python virtual environment along
+  with all the components necessary for integration development (including the
+  core agent used by the integrations). Some basic software might be needed to
+  install the python dependencies like `gcc` and `libssl-dev`.
+- Run `source venv/bin/activate` to activate the installed Python virtual
+  environment. To exit the virtual environment, run `deactivate`. You can learn
+  more about the Python virtual environment on the Virtualenv documentation.
+
+This is a quick setup but from that point you should be able to run the default test suit `rake ci:run`.
+To go beyond we advise you to read the full documentation [here](http://docs.datadoghq.com/guides/integration_sdk/).
+
 # Installing the Integrations
 
 The [Datadog Agent](https://github.com/DataDog/dd-agent) contains all core integrations from this repository, so to get started using them, simply install the `datadog-agent` package for your operating system.