Finish incomplete code and usage in helper class __Plugins__

[XerTheSquirrel]

In com.iopipe.__Plugins__ there is a method __searchPlugins() which does not have a full documentation header and is unused, it appears to be complete but it is not used. It should be used instead because its functionality in initializing internal plugins is much faster and if there is an issue with plugins included at run-time it will not cause the lambda to fail.

Therefor:

• Actually use it in the initializing constructor.
• Finish documenting it.

The code was added on commit 6ec9a92 which was on February 28, so it has been sitting unfinished and unused for almost 7 months.