remove R.version

Reasons to keep `R.version`:

  - Being able to type `R.version` into a REPL is occasionally useful.

Reasons to remove `R.version`:

  - It provides an additional and nonstandard way to access the version of the npm package: `require('x/package.json').version` works for every `x`.

  - It adds complexity to the release process (though this is largely mitigated by our automated release process).

  - In the near future we'll have custom builds, at which point a version string alone is not terribly useful. At that point I'd like to include the version string in the header along with the build options:

    ```javascript
    //     Ramda v0.9.0 custom build: +logic +math
    ```