Allow encryption of multiple variables

This allows you to do something like the following:

$ travis encrypt <<EOF
username=random
password=random2
EOF
Please add the following to your .travis.yml file:

  secure: "gfs4uN5PQcp..."
  secure: "asdfsdfDF..."

Pro Tip™: You can add it automatically by running with --add.
Fix interactive secure env var output
Add a flag for parsing each line as its own input
Make regexp in spec more robust

^...$ just matches any line in the string, \A...\Z makes sure that this
is matching the entire string.
let it generate accessor for line splitting automatically
improve output
Merge branch 'master' into hh-multiline-encrypt

Conflicts:
	lib/travis/cli/encrypt.rb
Merge pull request #5 from travis-ci/hh-multiline-encrypt

Allow encryption of multiple variables