feat(core): EncodingHelpers from posh-git

 - Used to ensure we read/write text files properly
feat: Posh-GitHub / VsVars $PROFILE encoding

 - function taken from posh-github, allow us to reliably
   select the appropriate encoding for writing to $PROFILE
fix(Posh-VsVars): better post-install message
chore: release Posh-VsVars 0.0.3
feat(Posh-GitHub): better post-install message
chore(Posh-GitHub): release 0.0.2