added git swap files to gitignore
use /sys instead of ifconfig

ifconfig in some distributions doesn't provide the RX and TX
informations (i.e. Arch), to get it working on every distro we can use
information that kernel provides via
/sys/class/net/$interface/statistics/[tr]x_bytes
Merge pull request #1 from everplays/fix-missing-rx-tx-info-in-ifconfig

Fix missing rx tx info in ifconfig