fix(plug-in): use absolute paths to reference entry points

Closes #52
fix(plug-in): revert conditional rebuild on change

This broke change detection for external resources included via brfs.

Instead of relying on the logic we must rely on debouncing the bundle
operation to suppress the double bundle.

The delay before an actual bundling operation is triggered may now be
configured via a browserify bundleDelay property in the karma
configuration.

Related to #69
feat(plug-in): add configure hook

This commit removes the prebundle hook to configure and adds the
prebundle event that may be used to perform additional configuration.

This allows users to reliably hook into the bundling process in
browserify@7 times.

Closes #63
feat(integration): add config hints