message: add 'core-test' npm script
diff: "scripts": {
  "browserify": "./node_modules/.bin/browserify lib/index.js --standalone blockstack -o ./tests/browserTests/bundle.js",
  "compile": "rm -rf lib; babel --presets es2015 src -d lib",
  - "compile-tests": "rm -rf tests/unitTests/lib; babel --presets es2015 tests/unitTests/src -d tests/unitTests/lib",
  + "compile-tests": "rm -rf tests/unitTests/lib; rm -rf tests/coreTests/lib; babel --presets es2015 tests/unitTests/src -d tests/unitTests/lib; babel --presets es2015 tests/coreTests/src -d tests/coreTests/lib;",
  "prepublish": "npm run compile",
  "release": "npm version patch && npm publish",
  "dev-auth": "npm run compile; npm run browserify; node ./tests/browserTests/auth-server.js",
  "dev-proofs": "npm run compile; npm run browserify; node ./tests/browserTests/proofs-server.js",
  - "test": "npm run compile; npm run compile-tests; npm run browserify; node ./tests/unitTests/lib/index.js"
  + "test": "npm run compile; npm run compile-tests; npm run browserify; node ./tests/unitTests/lib/index.js",
  + "core-test": "npm run compile; npm run compile-tests; npm run browserify; node ./tests/coreTests/lib/index.js"
  },
  "repository": {
  "type": "git",
  