Add guard to prevent more than one instance of bitcore

index.js

@@ -1,5 +1,26 @@
 var bitcore = module.exports;
 
+// module information
+bitcore.version = 'v'+require('./package.json').version;
+
+var inBrowser = typeof process === 'undefined' || typeof process.versions === 'undefined';
+if ((inBrowser && window._bitcore) || (!inBrowser && global._bitcore)) {
+  var versions = bitcore.version + ' and ' + inBrowser ? window._bitcore : global._bitcore;
+  var message = 'More than one instance of bitcore found with different versions: ' + versions;
+  if (inBrowser) {
+    message += '. Make sure any scripts included don\'t contain their own bitcore bundle.';
+  } else {
+    message += '. Make sure there are no version conflicts between package.json files of your '
+            + 'dependencies. This could also happen when a package depends on a git repository.';
+  }
+
+  throw new Error(message);
+}
+if (inBrowser) {
+  window._bitcore = bitcore.version;
+} else {
+  global._bitcore = bitcore.version;
+}
 
 // crypto 
 bitcore.crypto = {};
@@ -54,6 +75,3 @@ bitcore.deps._ = require('lodash');
 // Internal usage, exposed for testing/advanced tweaking
 bitcore._HDKeyCache = require('./lib/hdkeycache');
 bitcore.Transaction.sighash = require('./lib/transaction/sighash');
-
-// module information
-bitcore.version = 'v'+require('./package.json').version;