Check if tkellem is running first on tkellem start

Make sure tkellem isn't already running when the user types
tkellem start. If it is running already, print out a relevent
message and exit instead of daemonizing another instance.

Fixes #31
Rename running? to abort_if_running

Follow ruby naming convention. This method originally
returned a boolean, but I changed what the method did
and forgot to rename the method appropriately.
Merge pull request #32 from slottermoser/check-before-daemonizing

Check if tkellem is running first on tkellem start