Add hints to README on where to find scan results

[hmeine]

Since BANG is by default writing output to ~/tmp and not to the current directory, it may easily happen that a new user wonders where to look for the resulting report. (See issue #149)

[armijnhemel]

Actually this is a setting in the configuration file:

https://github.com/armijnhemel/binaryanalysis-ng/blob/master/src/bang.config#L12

[hmeine]

Yes, you probably did not look at my patch yet? I suggested pointing to that from the README.