Ejson secret base64 encoding issue

[alexcurtin]

This PR is to address issue #192 .

As Kubernetes >= 1.8 requires the yaml to no longer have a \n in it, we'll need to utilize Ruby's Base64.strict_encode64() to encode with no new lines. @KnVerey

# irb
:007 > str = "aooajsdjadad"
 => "aooajsdjadad"
 :008 > Base64.encode64(str)
 => "YW9vYWpzZGphZGFk\n"
 :009 > Base64.strict_encode64(str)
 => "YW9vYWpzZGphZGFk"

Docs: http://ruby-doc.org/stdlib-2.4.2/libdoc/base64/rdoc/Base64.html#method-i-strict_encode64

[jshapiro26]

I've made these changes locally as well and can confirm it has resolved this issue for me.

[KnVerey]

Thanks for the PR! Normally I'd request a regression test, but a local run shows several existing tests would fail on v1.8 without this patch (and we'll have 1.8 CI really soon!).