Add LEIN_NO_USER_PROFILES to avoid user profiles

When set, this environment var will prevent user level profiles from
loading.
Merge pull request #1616 from hugoduncan/feature/add-no-user-profiles

Add LEIN_NO_USER_PROFILES to avoid user profiles
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of github.com:CraZySacX/leiningen