Use RC in version string.

package.json

@@ -2,7 +2,7 @@
     "name": "typescript",
     "author": "Microsoft Corp.",
     "homepage": "http://typescriptlang.org/",
-    "version": "3.0.0",
+    "version": "3.0.0-rc",
     "license": "Apache-2.0",
     "description": "TypeScript is a language for application scale JavaScript development",
     "keywords": [
@@ -112,4 +112,4 @@
         "path": false
     },
     "dependencies": {}
-}
+}

src/compiler/core.ts

@@ -3,7 +3,7 @@ namespace ts {
     // If changing the text in this section, be sure to test `configureNightly` too.
     export const versionMajorMinor = "3.0";
     /** The version of the TypeScript compiler release */
-    export const version = `${versionMajorMinor}.0-dev`;
+    export const version = `${versionMajorMinor}.0-rc`;
 }
 
 namespace ts {