Update the build for 1.1.3

The protonmail bridge v1.1.3 changes a couple of things - how you log in (username vs. email) and the bridge binary name. This updates to build using those params. It also appears to switch xz for gz (although that may be an artifact of my pacman config). I also added a .gitignore file so that build artifacts and downloaded files don't make the source tree dirty in git.

This was built and tested on Pop! OS 18.04 (Ubuntu 18.04), so it does need to be tested on other distros.