first commit with submodules SusyCommon, SusyNtuple

Using the n0145 tags as a starting point. Commands used:
```
mkdir prod subm
git submodule add git@github.com:gerbaudo/SusyNtuple.git prod/SusyNtuple
git submodule add git@github.com:gerbaudo/SusyCommon.git prod/SusyCommon
cd prod/SusyNtuple/
git checkout SusyNtuple-00-01-04
cd ../SusyCommon/
git checkout SusyCommon-00-01-04-02
cd ..
git commit

```
adding the submodules within the directory `prod`.
The idea is to have again one directory to compile stuff (`prod`) and
one to submit jobs (`subm`).
use n0145 tags: SusyNtuple-00-01-04 and SusyCommon-00-01-03
import setup_area.sh from gerbaudo/susynt-prod-log
update readme
update gitignore (ignore external packages)