Add Counterclockwise integration

At the cost of adding a little noise at the start of each file, this change makes it possible to enable docstrings and autocompletion in Eclipse (and, I suppose, other editors).

In my experience trying to get people to learn Clojure, Counterclockwise has been a great asset since Eclipse is already well-known in the Java world and CCW now has [a ready-to-use bundle for each major platform](http://standalone.ccw-ide.org).

With this patch, the clojure-koans project can be easily cloned and imported from the standalone CCW (which includes the git plugin); having a namespace declaration in each file allows the user to use the interactive features of CCW (a beginner probably only needs CTRL+ALT+S for evaluating the whole file) and to get access to the docstrings as tooltips.

As a reference, here are the instruction notes I have written for people wanting to learn Clojure inside my company:

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The easiest way to get started with the Clojure syntax is probably the [online Clojure koans](http://clojurescriptkoans.com). For better syntax highlighting, formatting, and docs, install the koans locally with the following steps:

1. Download the [Counterclockwise bundle](http://standalone.ccw-ide.org) for your platform.
2. Create a folder and unzip the bundle inside it.
3. Open the Counterclockwise executable.
4. Import [my fork of the Clojure Koans](https://github.com/gaverhae/clojure-koans) project into Eclipse. The git plugin is included in Counterclockwise. (Click Window -> Open Perspective -> Other... -> Git Repository Exploring -> Clone a git repository -> git@github.com:gaverhae/clojure-koans.git -> Next -> Next -> Choose path and click Finish -> Right click on the repository -> Import Projects... -> Next -> Finish.)
5. In the Java perspective, right click on the project and choose Leiningen -> Generic Leiningen Command Line and replace "<task>" with "koan run". This sets up a program that will check the koans every time you save a file, and tell you which is the first koan that is not complete yet.
6. Still in the Java perspective, open the first koan (01_equalities.clj) and press CTRL+ALT+S to evaluate the file in a newly created REPL. This will enable documentation tooltips and autocompletion features.

Within Counterclockwise, CTRL+ALT+S evaluates the active file and CTRL+ENTER evaluates the top-level form under the cursor. Try it out, it'll be clearer than trying to explain that here.

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It's a bit more than "unzip and run", but they also end up with a complete development environment ready to go. Note that this patch also solves issue #68 and probably any other editor, as it makes the project sort of "standards compliant".