Read Bower paths from nearest .bowerrc

[nguyenjustin214-lab]

Fixes #22.

This updates Bower file discovery so callers do not have to pass paths.bowerDirectory/paths.bowerJson manually when those values can be discovered from the manifest path. If explicit options.paths are provided, those still take precedence.

Changes:

• Walk upward from the manifest file to find the nearest .bowerrc or bower.json, then pass that directory to main-bower-files.
• Stop assuming the component directory is literally named bower_components when matching package names, so custom .bowerrc directories work.
• Keep Bower package exclusions as flat package names and add an integration regression for .bowerrc discovery.

Verification:

• npm test
• npm run jshint
• git diff --check