Proposal: Easier debugging across related projects

I propose we make it easier to locally debug interdependent projects.

I've run into three instances so far (outlined below) where I've had to modify source code when, ideally, I should have just been able to add my local dependency to `package.json` and that's it.

We need to facilitate these common workflows (probably a couple `if` checks in the various source codes would suffice) and should document any additional steps in the appropriate `CONTRIBUTING.md`

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#### 1: `donejs/donejs` + `donejs/generator-donejs`

https://github.com/donejs/generator-donejs/issues/135#issuecomment-284203738

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#### 2: `donejs/donejs` + `donejs/cli`

https://github.com/donejs/cli/pull/82#issuecomment-289615878

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#### 3: `bit-docs/bit-docs` + project using `bit-docs` + local html generation plugin

I have to publish my package:

https://www.npmjs.com/package/bit-docs-website-theme

Just in order to use it locally. Seems like I should be able to do:

```
"bit-docs-website-theme": "file:///Users/leoj/src/bitovi/wip/bit-docs-website-theme"
```

In `package.json`, but that causes a 404 failure because some part of code insists on DLing from npm when I do `./node_modules/bit-docs/bin/bit-docs -fd`.

So, I was forced to publish this package just to test it out, because I can't locate the bit of code that is attempting npm download, and making everything fail.

It's probably a similar case to that which I ran into when trying to locally debug the DoneJS CLI:

https://github.com/donejs/generator-donejs/issues/135#issuecomment-289917095

It seems like there must be some facility for debugging packages locally, without having to publish to npm constantly?

There must be a better way than adding `INJECTING LOCAL COPY` hacks (like I do in the link below), Right?

https://github.com/donejs/cli/pull/82#issuecomment-289615878

If not, a facility to allow local debugging would be a great thing to add into the frameworks in these places where it currently forces the use of remote npm.