added: more path candidates for Chrome/Chromium in Linux

As I'm using ArchLinux, the paths for Chrome(dev-channel) and Chromium are "/usr/bin/google-chrome-unstable" and "/usr/bin/chromium" respectively, neither of which is included in this original source code.

So I did some investigations about common Linux distributions and made this pull request to fix this problem (at least for me it's fixed).

Also, instead of showing "Could not find chrome" and exiting the program, shall we add a dialog to let the user pick a browser path when it can not be automatically detected?