Merge pull request #1120 from JamesYongQiaoWang/enhanceReadMe

Enhance the README to install swarm from source

README.md

@@ -21,43 +21,52 @@ The goal is to provide a smooth out-of-the-box experience for simple use cases,
 allow swapping in more powerful backends, like Mesos, for large scale production
 deployments.
 
-## Installation and documentation
+## Installation for Swarm Users
 
-Full documentation [is available here](http://docs.docker.com/swarm/).
+For installing swarm for using in your environment, use the Docker Swarm
+documentation on [docs.docker.com](http://docs.docker.com/swarm/).
 
-## Development installation
+## Installation for Swarm Developers
 
-You can download and install from source instead of using the Docker
-image. Ensure you have golang, godep and the git client installed.
+Developers should always download and install from source rather than
+using the Docker image.
 
-**For example, on Ubuntu you'd run:**
+### Prerequisites
 
-```bash
-$ apt-get install golang git
-$ go get github.com/tools/godep
-```
+1. Beginning with Swarm 0.4 golang 1.4.x or later is required for building Swarm. 
+Refer to the [Go installation page](https://golang.org/doc/install#install)
+to download and install the golang 1.4.x or later package.
+> **Note**: On Ubuntu 14.04, the `apt-get` repositories install golang 1.2.1 version by
+> default. So, do not use `apt-get` but install golang 1.4.x manually using the
+> instructions provided on the Go site.
+
+2. Install [Git](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git).
 
-You may need to set `$GOPATH`, e.g `mkdir ~/gocode; export GOPATH=~/gocode`.
+3. Install [godep](https://github.com/tools/godep).
 
-**For example, on Mac OS X you'd run:**
+### Clone and build Swarm
+
+> **Note** `GOPATH` should be set when install godep in above step.
+
+Install the `swarm` binary in the `$GOPATH/bin` directory. An easy way to do this 
+is using the `go get` command.
 
 ```bash
-$ brew install go
-$ export GOPATH=~/go
-$ export PATH=$PATH:~/go/bin
-$ go get github.com/tools/godep
+$ go get github.com/docker/swarm
 ```
 
-Then install the `swarm` binary:
+You can also do this manually using the following commands:
 
 ```bash
 $ mkdir -p $GOPATH/src/github.com/docker/
 $ cd $GOPATH/src/github.com/docker/
 $ git clone https://github.com/docker/swarm
 $ cd swarm
-$ godep go install .
+$ $GOPATH/bin/godep go install .
 ```
 
+Then you can find the swarm binary under `$GOPATH/bin`.
+
 From here, you can follow the instructions [in the main documentation](http://docs.docker.com/swarm/),
 replacing `docker run swarm` with just `swarm`.