Fix: client plugins crashing hoodie server in Windows (#867)

In Windows adding a client plugin as described in http://docs.hood.ie/en/latest/guides/plugins.html will crash hoodie server with error
Error: Cannot find module 'C:UsersUserdevhoodie-serverhoodieclient' as backslashes in Windows paths are collapsed when building the string hoodieBundleSource. The fix replaces backslashes in the paths with forward slashes which work both in Linux and Windows.

server/plugins/client/bundle.js

@@ -34,6 +34,7 @@ function bundleClient (hoodieClientPath, bundleTargetPath, options, callback) {
 
   var plugins = [path.resolve('hoodie/client')]
     .concat(pluginPaths)
+    .map(p => p.replace(/\\/g,"/") )  // fix backslashes in Windows paths
     .filter(checkModule)
 
   var getPluginsModifiedTimes = plugins.map(function (pluginPath) {