message: Make Environments immutable
diff: const common = require('./common');
  const bitgo = module.exports;
  bitgo.BitGo = require('./bitgo.js');
  -bitgo.Environments = common.Environments;
  // Expose bitcoin and sjcl
  bitgo.bitcoin = require('./bitcoin');
  @@ -14,6 +13,10 @@ bitgo.sjcl = require('./sjcl.min');
  bitgo.bs58 = require('bs58');
  bitgo.Buffer = Buffer;
  +// Expose environments
  +const _ = require('lodash');
  +bitgo.Environments = _.cloneDeep(common.Environments);
  +
  /**
  * Set the network, i.e. either "bitcoin" for production with real bitcoin, or
  * "testnet" for development with testnet bitcoin.
  