add disable atom's default tree-view on file-tree package load

[knowbody]

This is in reference to #3

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[ssorallen]

Could you keep a reference to the config object to simplify this?

var coreDisabledPackages = atom.config.get('core.disabledPackages');
if (coreDisabledPackages.length === 0 ||
    coreDisabledPackages.indexOf('tree-view') === -1) {
  atom.config.pushAtKeyPath('core.disabledPackages', 'tree-view');
}

[knowbody]

fixed

[knowbody]

@ssorallen anything else you would like me to change?

[ssorallen]

@knowbody, we are looking at some additions to your pull request internally. Specifically, when you disable the nuclide-file-tree package the bundled Atom file-tree should re-enable.

[knowbody]

👍 cool, @ssorallen let me know if I can help somehow

[knowbody]

@ssorallen this can be closed as you fixed it internally now with:

// We need to check if the package is already disabled, otherwise Atom will
// add it to the 'core.disabledPackages' config multiple times.
if (!atom.packages.isPackageDisabled('tree-view')) {
  atom.packages.disablePackage('tree-view');
}

[ssorallen]

Great. Thanks for pull request, it prompted us to make nuclide-file-tree interact with Atom's tree-view better. If you still have problems, please comment or re-open the PR/issue.