use default options when none provided

[ecwyne]

fixes #28

[ecwyne]

@thebigredgeek I wasn't sure if you wanted the dist changes committed or not. Let me know if there are any changes you'd like me to make!

Thanks for an amazing package!

[lxcid]

What is the reason to have 2 error config though? In constructor I mean

[ecwyne]

const FooError = createError(baseConfig);

throw new FooError(config);

baseConfig provides all of the defaults while config may override or add additional values.

[lxcid]

Thanks @ecwyne, I figure out on the side though. I came up with a different PR which is mostly identical with yours except with the order the config get merged though, but a lot of it references on the existing PRs.

Thanks for the quick explanation!

[thebigredgeek]

I believe this functionality is now already implemented. I am about to release 1.8 so once you get a chance to upgrade please let me know if this PR is still necessary