Block version-specific docs from search engines

Stable, beta and nightly URLs remain

Author: kornelski

src/doc/robots.txt

@@ -1,21 +1,6 @@
 User-agent: *
-Disallow: /0.3/
-Disallow: /0.4/
-Disallow: /0.5/
-Disallow: /0.6/
-Disallow: /0.7/
-Disallow: /0.8/
-Disallow: /0.9/
-Disallow: /0.10/
-Disallow: /0.11.0/
-Disallow: /0.12.0/
-Disallow: /1.0.0-alpha/
-Disallow: /1.0.0-alpha.2/
-Disallow: /1.0.0-beta/
-Disallow: /1.0.0-beta.2/
-Disallow: /1.0.0-beta.3/
-Disallow: /1.0.0-beta.4/
-Disallow: /1.0.0-beta.5/
+Disallow: /1.
+Disallow: /0.
 Disallow: /book/first-edition/
 Disallow: /book/second-edition/
 Disallow: /stable/book/first-edition/