Need epub as part of the releases

[commjoen]

In order to speed up the delivery of the epubs, it would be best if we can make sure that ebups are generated by travis as well.
For this we want to use the Owasp Books project.

[commjoen]

We have chosen to use the gitbook-cli to create the epub, mobi and pdf. This means that we have to manually update the book at leanpub... So it is now part of our release. Leanpub and gitbook show not wanting to collaborate. So will close this issue.

If people want to get the epub/mobi file without leanpub: check the readme saying

Clone the repository and run the gitbook generator. This produces PDF, Epub and Mobi files in the "Generated" subdirectory.
$ git clone https://github.com/OWASP/owasp-mstg/
$ cd owasp-mstg/Tools/
$ ./gitbookandpdf.sh