Major changes:

• code cleanup (mostly thanks to code analysis tools)
• added Travis-CI tests
• key pinning (configurable in advanced options) is used by default (only possible with curl > 7.39)
• extended the CryptTool with more features of libsodium (e.g. constant-time string comparison or hex2bin/bin2hex), it is strongly recommend to use them

All changes: a43ff5a...master

This release is not yet an official one released by Threema on their website (that's why I've marked it as a pre-release). However I had to make a release now and Threema acknowledged the version number, so hopefully this will prevent version number conflicts.
For now feel free to use it. It is stable and in most cases backwards-compatible.