- install softcover with gem install command
- setup installation of texlive latex distribution and added usepackage todonotes

Perform a texlive installation with apt-get (is slow but worked) and all extra packages
they are used from softcover.

Added \usepackage command to the preamble.tex file. So that \todo and \missingfigures
command are available
- added encrypted softcover api key to support publishing from travis