The minimum go version to build packer is 1.2, not 1.1.

Change the documentation accordingly. 'ne' template function was added as part of go 1.2.
http://golang.org/doc/go1.2#text_template
Verify go version when building packer.

Check if the installed version is greater than the required version. Error out if that's not the case
Merge pull request #719 from sudharsh/go_minver_verify

The required go version to build packer seems to be 1.2