ui/tree doesn't support file-icons package about nuclide

[ssorallen]

@balaji, for now we are removing the icon-file-code usage inside Nuclide so this package will work. We can look at a more robust API for file tree customization later.

[balaji]

Doing the first item solves the problem w.r.t file-icons package because icon-file-text class is already present (through atom-helpers package).

Are you suggesting that in future there will be customizations on the tree view based on this class or that the class itself will go away?

[balaji]

My bad. Sorry. I didn't check the code close enough. Looks like we add icon-file-code for desired file extensions.

  ...
  } else if (CODE_EXTENSIONS.hasOwnProperty(ext)) {
    typeClass = 'icon-file-code';
  } else {
    typeClass = 'icon-file-text';
  }

[ssorallen]

This is fixed with commit 4041973. Nuclide's file tree does less customization to allow the file-icons package to work.