Spelling & checks

.github/CONTRIBUTING.md

@@ -50,7 +50,7 @@ can quickly merge or address your contributions.
 
 ## Setting up Go
 
-If you have never worked with Go before, you will have to install it's
+If you have never worked with Go before, you will have to install its
 runtime in order to build packer.
 
 1. [Install go](https://golang.org/doc/install#install)
@@ -61,7 +61,7 @@ If/when you have go installed you can already `go get` packer and `make` in
 order to compile and test Packer. These instructions target
 POSIX-like environments (Mac OS X, Linux, Cygwin, etc.) so you may need to
 adjust them for Windows or other shells.
-The instructions below are for go 1.7. Earlier versions of Go are no longer supported.
+The instructions below are for go 1.7. or later.
 
 
 1. Download the Packer source (and its dependencies) by running