Exit on failure about mermaid.cli

[prantlf]

The main program body is asynchronous, but it does not handle errors thrown during the graph processing. Such errors are (still) handled by Node.js, but his approach is not recommended, hence the warnings printed by Node.js. The process hangs, because there are still callbacks waiting. (Chrome is running.)

I created PR #66 to fix this problem by terminating the process with a non-zero exit code.

[pturley]

I agree, this would be really nice to have

[hasanalrasyid]

Is this behavior coming from the main node.js?
The error said
"(node:7014) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code."

Really wished for that not so far future to come soon...