bump version (#532)

* bump version

* Update version.json

Rx.NET/Source/version.json

@@ -1,9 +1,8 @@
 {
-  "version": "4.0.0-preview.3.build.{height}",
+  "version": "4.1.0-preview.{height}",
   "publicReleaseRefSpec": [
     "^refs/heads/master$", // we release out of master
-    "^refs/heads/rel/v\\d+\\.\\d+", // we also release tags starting with vN.N
-    "^refs/tags/v\\d+\\.\\d+" // we also release tags starting with vN.N
+    "^refs/heads/rel/v\\d+\\.\\d+" // we also release branches starting with rel/vN.N
   ],
   "nugetPackageVersion":{
     "semVer": 2