Tweak .app.src file

The list of modules is added by rebar,
as well as calculating a sensible (useful) version
based on latest git tag and current commit.

The .app file with this change may look something like:
```
{application,erltrek,
             [{description,"An Erlang Star Trek game"},
              {vsn,"baselevel_20140313-2-gb1b4721"},
              {env,[]},
              {registered,[erltrek_game,erltrek_event]},
              {applications,[kernel,stdlib]},
              {modules,[e,erltrek_calc,erltrek_event,erltrek_game,
                        erltrek_klingon,erltrek_move,erltrek_phaser,
                        erltrek_scan,erltrek_setup,erltrek_terminal,
                        tinymt32]}]}.
```
Add application infrastructure (#5)