Fix dotCloud link

dotCloud no longer exists, and since this part of the
readme is refering to "where it all started", replaced
the link with an archive link around the time that
Docker was publicly announced.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

README.md

@@ -13,12 +13,12 @@ databases, and backend services without depending on a particular stack
 or provider.
 
 Docker began as an open-source implementation of the deployment engine which
-powers [dotCloud](https://www.dotcloud.com), a popular Platform-as-a-Service.
-It benefits directly from the experience accumulated over several years
-of large-scale operation and support of hundreds of thousands of
-applications and databases.
+powered [dotCloud](http://web.archive.org/web/20130530031104/https://www.dotcloud.com/),
+a popular Platform-as-a-Service. It benefits directly from the experience
+accumulated over several years of large-scale operation and support of hundreds
+of thousands of applications and databases.
 
-![](docs/static_files/docker-logo-compressed.png "Docker")
+![Docker logo](docs/static_files/docker-logo-compressed.png "Docker")
 
 ## Security Disclosure