src: establish context on PCSCLite constructor
src: establish context on PCSCLite constructor

- Remove SCardEstablishContext from get_card_readers.
- Initialize m_status_thread to NULL so calling PCSCLite destructor does not
  crash in case the thread has not been launched. For example when
  SCardEstablish context fails
- Thanks to Ludovic Rousseau for pointing that out @
  https://github.com/santigimeno/node-pcsclite/pull/15#issuecomment-56222251.

Bangsadrengur/node-pcsclite,santigimeno/node-pcsclite,TimeTravelersHackedMe/node-pcsclite,durai145/node-pcsclite,TimeTravelersHackMe/node-pcsclite,Bangsadrengur/node-pcsclite,santigimeno/node-pcsclite,Bangsadrengur/node-pcsclite,LudovicRousseau/node-pcsclite,durai145/node-pcsclite,LudovicRousseau/node-pcsclite,santigimeno/node-pcsclite,TimeTravelersHackMe/node-pcsclite,TimeTravelersHackedMe/node-pcsclite,TimeTravelersHackMe/node-pcsclite,durai145/node-pcsclite,TimeTravelersHackedMe/node-pcsclite,LudovicRousseau/node-pcsclite