Use local_repository from lockfile in install()

This fixes an issue where `lockjar install` was ignoring the local_repository set in the lockfile. That basically meant that it installed into the default repo location (usually ~/.m2/repository). However, a subsequent LockJar.load() would try to read from local_repo, and (if different from the default repo) not find the Jars.

This should also fix https://github.com/mguymon/lock_jar/issues/15 - I actually noticed this while trying to get my project to build under Travis-CI.