fix constant label width changes

using pango and padding
Update README.md
cherry pick 17918ab711a43b7b72bdfafd6634f713f5d3b9fc
Merge branch 'master' of https://github.com/kjyv/indicator-netspeed
allow selecting the network interface
growing width as needed

get rid of bytes display, less jittering
optional positioning to the left of app indicators

don't display bytes separately anymore because of jittering
update readme
typos