[JS] Define code entry point for integration testing

[toddfarmer]

Note: This issue was originally created as ARROW-1502. Please see the migration documentation for further details.

Original Issue Description:

This needs to provide a similar command line interface to the Java and C++ integration testing entry points:

• Command: convert JSON to Arrow, or Arrow to JSON
• Arrow file path
• JSON file path

[toddfarmer]

Note: Comment by Paul Taylor (paul.e.taylor): resolved in https://github.com/apache/arrow/pull/1482