Improved install and update instructions (#3)

* [add] Making reference to go supported versions

Author: filipecosta90

README.md

@@ -10,17 +10,33 @@ Several aspects can dictate the overall system performance, like the:
 - Number of subscribers per channel (controlled on subscriber)
 - Subscriber distribution per shard and channel (controlled on subscriber)
 
-## Installation
 
-The easiest way to get and install the Subscriber Go program is to use
-`go get` and then `go install`:
-```bash
-# Fetch this repo
+## Getting Started
+
+### Installing
+This benchmark go program is **know to be supported for go >= 1.11**. 
+The easiest way to get and install the Subscriber Go program is to use `go get` and then `go install`:
+
+```
 go get github.com/filipecosta90/pubsub-sub-bench
 cd $GOPATH/src/github.com/filipecosta90/pubsub-sub-bench
 make
 ```
 
+#### Updating 
+To update the Subscriber Go program use `go get -u` to retrieve the latest version:.
+```
+go get -u github.com/filipecosta90/pubsub-sub-bench
+cd $GOPATH/src/github.com/filipecosta90/pubsub-sub-bench
+make
+```
+
+#### Limitations 
+
+There are know limitations on old go version due to the radix/v3 dependency, given that on old versions, 
+the go command in GOPATH mode does not distinguish between major versions, meaning that it will look for the package `package github.com/mediocregopher/radix/v3` instead of v3 of `package github.com/mediocregopher/radix`.
+Therefore you should only use this tool on go >= 1.11. 
+
 ## Usage of pubsub-sub-bench
 
 ```