"Current installation is invalid, please run NPM install first" because of bower component

We put bower dependencies in a specific folder, using `.bowerrc`. We installed Angular as a Bower dependency, and when I run `next-update` I get:

```
next-update - Tests if module's dependencies can be updated to latest version
version: 0.5.1
author: {"name":"Gleb Bahmutov","email":"gleb.bahmutov@gmail.com"}
checking if the current state works
ERROR: cannot find folder /home/nchambrier/Projects/LMTM/ooz/bower_components/angular
ERROR testing next working updates
Error: Current installation is invalid, please run NPM install first
at /home/nchambrier/.nvm/v0.10.32/lib/node_modules/next-update/src/next-update.js:35:26
at node.js:906:3
From previous event:
at checkDependenciesInstalled (/home/nchambrier/.nvm/v0.10.32/lib/node_modules/next-update/src/next-update.js:29:19)
at Object.checkCurrentInstall (/home/nchambrier/.nvm/v0.10.32/lib/node_modules/next-update/src/next-update.js:43:12)
at Object. (/home/nchambrier/.nvm/v0.10.32/lib/node_modules/next-update/index.js:129:38)
```

Obviously, if it looks for Angular in `./bower_components` it won't be found as there is no such folder.

`next-update` should either
- ignore bower dependencies (I thought it only checked npm dependencies)
- read `.bowerrc`

Start with src/next-update.js, especially checkDependenciesInstalled and checkCurrentInstall, then trace the call from index.js. Reproduce the failure with a .bowerrc that places Angular outside ./bower_components; done when the npm installation check no longer incorrectly rejects this setup, either by ignoring Bower dependencies or honoring the configured location.

Written by the indexing model from the issue text.