AppImage is not build in travis

[matejm]

Currently Travis-ci fails to build AppImage file. Using linuxdeployqt script, following error is displayed.

$ ./linuxdeployqt*.AppImage ./appdir/usr/share/applications/*.desktop -bundle-non-qt-libs -qmldir=.
fusermount: failed to open /etc/fuse.conf: Permission denied
fusermount: failed to access mountpoint /tmp/.mount_9jC3BW: Permission denied
Cannot mount AppImage, please check your FUSE setup.
You might still be able to extract the contents of this AppImage 
if you run it with the --appimage-extract option. 
See https://github.com/AppImage/AppImageKit/wiki/FUSE 
for more information
open dir error: Transport endpoint is not connected

AppImage file is not built and consequently not uploaded to GitHub Releases.

[probonopd]

Make sure FUSE is enabled and working. If you are building on Travis CI, use dist: trusty and sudo: true in .travis.yml.

[probonopd]

@matejm did you test #40 (comment)?

[matejm]

We already use dist: trusty. I overlooked that we should use sudo: true (currently we have sudo: required).
I have changed it now. commit.

[matejm]

As expected, error is exactly the same.

Because we changed our core encryption library .travis.yml definitely needs to be rewritten (#42). With readable travis file, it will be possible to debug this.