golang: Update to version 1.6 as the minimum

Etcd now requires golang version 1.6 or greater.

.travis.yml

@@ -1,7 +1,5 @@
 language: go
 go:
-  - 1.4.3
-  - 1.5.4
   - 1.6
   - 1.7
   - tip
@@ -13,8 +11,6 @@ matrix:
   fast_finish: true
   allow_failures:
     - go: tip
-    - go: 1.4.3
-    - go: 1.6
     - go: 1.7
 notifications:
   irc:

README.md

@@ -25,6 +25,7 @@ Please join the [#mgmtconfig](https://webchat.freenode.net/?channels=#mgmtconfig
 If you have a well phrased question that might benefit others, consider asking it by sending a patch to the documentation [FAQ](https://github.com/purpleidea/mgmt/blob/master/DOCUMENTATION.md#usage-and-frequently-asked-questions) section. I'll merge your question, and a patch with the answer!
 
 ## Quick start:
+* Make sure you have golang version 1.6 or greater installed.
 * Clone the repository recursively, eg: `git clone --recursive https://github.com/purpleidea/mgmt/`.
 * Get the remaining golang dependencies on your own, or run `make deps` if you're comfortable with how we install them.
 * Run `make build` to get a freshly built `mgmt` binary.
@@ -49,7 +50,7 @@ Bonus points if you provide a [shell](https://github.com/purpleidea/mgmt/tree/ma
 Feel free to read my article on [debugging golang programs](https://ttboj.wordpress.com/2016/02/15/debugging-golang-programs/).
 
 ## Dependencies:
-* golang 1.4 or higher (required, available in most distros)
+* golang 1.6 or higher (required, available in most distros)
 * golang libraries (required, available with `go get`)
 
         go get github.com/coreos/etcd/client