* get rid of deprecated sklearn package

* Update to tltk 1.8
* therefore call this version 1.2.0

* Allow Python installation to alternative target

Remove python stuff from Debian package and install into virtual

environment using pip instead.

Unfortunately INSTALL.md seems to be hard to understand for some people.

Thus try to point out even better, that the transcription-daemon needs to be
running when calling make test.

Update README.md and INSTALL.md for Version 1.0