Add badges and install info

Author: danielgtaylor

README.md

@@ -1,5 +1,7 @@
 # Metrics Library for Go
 
+[![Travis](https://img.shields.io/travis/istreamlabs/go-metrics.svg)](https://travis-ci.org/istreamlabs/go-metrics) [![Codecov](https://img.shields.io/codecov/c/github/istreamlabs/go-metrics.svg)](https://codecov.io/gh/istreamlabs/go-metrics) [![GitHub tag](https://img.shields.io/github/tag/istreamlabs/go-metrics.svg)](https://github.com/istreamlabs/go-metrics/releases) [![License](https://img.shields.io/github/license/istreamlabs/go-metrics.svg)](https://github.com/istreamlabs/go-metrics/blob/master/LICENSE)
+
 A library that provides an interface for sending metrics from your script, application, or service. Metrics consist of a name, value, and optionally some tags that are made up of key/value pairs.
 
 Multiple implementations are provided to allow for production, local development, and testing use cases. The following clients are available:
@@ -13,7 +15,17 @@ Client           | Description
 
 ## Example Usage
 
-Generally you will instantiate one of the above clients and then write metrics to it:
+Generally you will instantiate one of the above clients and then write metrics to it. First, install the library:
+
+```sh
+# If using dep, glide, godep, etc then use that tool. For example:
+dep ensure github.com/istreamlabs/go-metrics
+
+# Otherwise, just go get it:
+go get github.com/istreamlabs/go-metrics
+```
+
+Then you can use it:
 
 ```go
 import "github.com/istreamlabs/go-metrics"
@@ -29,7 +41,7 @@ client.WithTags(map[string]string{
 }).Incr("requests.count")
 ```
 
-The above code would result in `myprefix.requests.count` with a value of `1` showing up in DataDog. See the [`Client`](https://godoc.org/github.com/istreamlabs/go-metrics/#Client) interface for a list of available metrics methods.
+The above code would result in `myprefix.requests.count` with a value of `1` showing up in DataDog if you have [`dogstatsd`](https://docs.datadoghq.com/guides/dogstatsd/) running locally. See the [`Client`](https://godoc.org/github.com/istreamlabs/go-metrics/#Client) interface for a list of available metrics methods.
 
 Also provided are useful clients for testing. For example, the following asserts that a metric with the given name, value, and tag was emitted during a test: