Fix installing LINC-Switch after modifying rebar configuration

Sys.config file has been removed from the version control system but LINC
won't start without it. In face of that is need to be created manually.
(Motivated by FlowForwarding/LINC-Switch#242).
Merge pull request #2 from FlowForwarding/no-sys.config-error

Fix installing LINC-Switch after modifying rebar configuration