Nightly build

Note: The executable is made with pyinstaller. An unfortunate side effect is that some anti-virus software may falsely flag pyinstaller executables as malware. This is a known issue (https://github.com/pyinstaller/pyinstaller/issues?utf8=%E2%9C%93&q=is%3Aissue+virus) and unavoidable. If you prefer, you can not use this exe and instead run zoffline directly from the source code (2nd installation method in the README).