Add languages I've seen and those I've written code in.

Likely incomplete.

The 'written' list is hopefully in chronical order (time of first
writing code in the language).

README.md

* current:
    - [clojure](http://clojure.org): A modern Lisp on the JVM.
    - [haskell](http://haskell.org)
* seen: Bash, C, C++, Ruby, Python, Java, Erlang, J, Haskell, Clojure,
  Scala, Perl, Forth, ASM, Scheme
* written: Bash, C, Ruby, Python, Scheme, Haskell, Java, Erlang, Clojure