Possibility to build the library with only specific string functions

There are following string functions from **underscore.string** library that are usable for me:
- `trim`,
- `startsWith`,
- `endsWith`,
- `lines`.

But I don't want to include many other parsing stuff from it.
I think that having download builder like [jQueryMobile](http://jquerymobile.com/download-builder/) is very good in this case...