Allow components to refer to themselves.

[lynaghk]

Declaring the component name at the top of the let will allow the render
body to invoke the component.

declare for side-effects within a let is ugly, but better than the
alternatives:

• No way to replace let with letfn since the render body won't be
  calling itself.
• Putting the declare outside of the let would require the macro
  splicing, which is trickier to understand and requires more syntax

[lynaghk]

Note that I wasn't able to test this commit; boot gave me the following error:

kevin@nu:~/software/rum$ boot install
             clojure.lang.ExceptionInfo: java.lang.Exception: can't find jar file
    data: {:file
           "/var/folders/fm/fmgnykm11tjc0_g6jr1h7kch0000gn/T/boot.user4483160175845386140.clj",
           :line 23}
java.util.concurrent.ExecutionException: java.lang.Exception: can't find jar file
                    java.lang.Exception: can't find jar file
     boot.task.built-in/fn/fn/fn/fn                      built_in.clj:  625
                boot.core/run-tasks                          core.clj:  680
                                ...
               boot.user/eval786/fn  boot.user4483160175845386140.clj:   25
clojure.core/binding-conveyor-fn/fn                          core.clj: 1910
                                ...

I don't use boot; I installed it via homebrew:

kevin@nu:~/software/rum$ boot --version
#https://github.com/boot-clj/boot
#Wed Jun 10 15:49:26 PDT 2015
BOOT_CLOJURE_VERSION=1.6.0
BOOT_VERSION=2.0.0-rc14
#App version: 2.0.0