Implement print-libs command for hit

Use it as follows:

    $ hit print-libs default

To print all 'so' libraries. Or you can specify any suffix as follows:

    $ hit print-libs default --suffix so
    $ hit print-libs default --suffix dylib
    $ hit print-libs default --suffix dll
Merge pull request #150 from hashdist/print-libs

Implement print-libs command for hit