Can we specify the nodejs version we want to use

I notice that we specify the language in the configuration as such

```
# Appended to the user agent of the KCL. Does not impact the functionality of the
# KCL in any other way.
processingLanguage = nodejs/0.10
```

If i I have nopdejs v4.2.1 installed how am i able to specify that in the configuration file.

Start by locating the configuration entry for processingLanguage and tracing how its value is used in the Kinesis client user agent. Confirm whether a Node.js version such as 4.2.1 can be supplied there, and document or test the supported configuration behavior; the issue names no files or tests.

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