Update the version to 1.3.0

Author: hajimehoshi

_docs/public/index.html

@@ -37,7 +37,7 @@
 </style>
 <a href="https://github.com/hajimehoshi/ebiten"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://camo.githubusercontent.com/365986a132ccd6a44c23a9169022c0b5c890c387/68747470733a2f2f73332e616d617a6f6e6177732e636f6d2f6769746875622f726962626f6e732f666f726b6d655f72696768745f7265645f6161303030302e706e67" alt="Fork me on GitHub" data-canonical-src="https://s3.amazonaws.com/github/ribbons/forkme_right_red_aa0000.png"></a>
 <h1>Ebiten (海老天)</h1>
-<p>Stable version: v1.3.0-rc1 / Development version: v1.4.0-alpha</p>
+<p>Stable version: v1.3.0 / Development version: v1.4.0-alpha</p>
 <ul>
   <li>A simple SNES-like 2D game library in Go</li>
   <li>Works on

version.txt

@@ -1 +1 @@
-1.3.0-rc1
+1.3.0