The systray quit is being fixed in our fork of the getlantern/systray.

Create a systray.pid file to check if another systray is in execution
and only one systray is allowed to be running.

- Resolves: #17

While we wait to get the fix to the hide menu items issue merged upstream let's
use our own fork of the library.

- Resolves: #8

- Resolves: #16

Try different known paths for the svg file.

- Resolves: #10

- Resolves: #14

Using golang.org/x/text, wich is still in early stages of development,
but seems to work good enough for our needs.

- Resolves: #2

- Resolves: #12

- Resolves: #7

- Resolves: #6