Read from local .POM file

Hi,

these changes were made during a tentative build of a Java package for OpenSuSE. The package did not exist on JPP, so I amended pom2spec to make it read a locally stored pom.xml file. Then, I had planned to use the resulting .spec that had to fetch dependencies from JPP and use ant or maven to build the package jar.

But, being the packaged software tested with specific dependencies versions, and given the burden of creating many packages for each dependency, I went for the binary package route. My results are on [the buildservice](https://build.opensuse.org/package/show/home:vjt:ifad/couchdb-lucene).

Anyway, I think that this change to pom2spec may be useful.