Updating Node.js binary to 0.10.21

* parameterizing it's version
* tweeking a bit with it's messages
Removing repetitive bower version message on deploy.

When building the application the following messages appear:

-----> Writing config/database.yml to read from DATABASE_URL
-----> Using bower version: 1.2.7
-----> Installing JavaScript dependencies using bower 1.2.7

There is an unecessary repetition on bower version, this removes this
message, like:

-----> Writing config/database.yml to read from DATABASE_URL
-----> Installing JavaScript dependencies using Bower 1.2.7
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