Making a valid gemspec for bundler installs from github by re-using existing markdown README for rdoc.

Saw the open sourcing in my feed! Congrats. I am taking a kick at the can with it and I fixed a little bundler error I got:

```
smithy at /Users/jody/.rbenv/versions/1.9.2-p290/lib/ruby/gems/1.9.1/bundler/gems/smithy-677ced904db4 did not have a valid gemspec.
This prevents bundler from installing bins or native extensions, but that may not affect its functionality.
The validation message from Rubygems was:
  ["README.rdoc"] are not files
```