Add option to use .importjs-root file to detect project root

[mikabytes]

As discussed in #546

This adds the option to create a file .importjs-root to allow for ImportJS to detect the root of the project.

This is useful for projects that don't have a package.json, such as those that use native ES modules only.

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Hm, could someone help me understand what's going on with Travis? Those errors seem unrelated to my changes, and all tests pass when I run them locally.

[trotzig]

Looks like failures are coming from Node v6&7. Are you able to repro locally with one of those versions? If not I think it’s safe to cut out Node < 8 (I can make that happen as part of releasing this change).

[trotzig]

Btw, thanks for making a PR! Quick turnaround! 👏

[mikabytes]

Happy to contribute to such an awesome tool. One of the few I use every hour of the day ;)

I have confirmed this is an issue with Node 7 (probably also holds true for 6). Also confirmed the same test results in master branch, so this is not related to this PR.

Always happy to drop support. You have my encouragement :)

[trotzig]

After some CI/build issues I was finally able to get a release shipped. This change is included in v4. 🚢

[trotzig]

What editor are you using? I'm a vim user myself, but I made sure to bump the Atom plugin as well (which is the only plugin with a direct dependency on the import-js npm lin--others rely on a globally installed command).

[mikabytes]

Awesomeness! Quick turnaround indeed.

I'm a devout Vim user, and although I don't like to bloat my editor with YouCompleteMe and such, ImportJS is really bringing that warm breeze into my work environment. Especially when working with libs that require lots of small little imports; Redux Saga, Yup, etc.

Ha en fin vinterdag! Snart läggdags här i Filippinerna ;)