fixes issue #17
fixes issue #17

This addresses an issue with installation of setuptools during initial 'make env'.

'make env' also tries to deal more gracefully with previous run of the target.

QISKit/qiskit-sdk-py,atilag/qiskit-sdk-py,QISKit/qiskit-sdk-py,atilag/qiskit-sdk-py,ChristopheVuillot/qiskit-sdk-py,ChristopheVuillot/qiskit-sdk-py,QISKit/qiskit-sdk-py,ChristopheVuillot/qiskit-sdk-py,atilag/qiskit-sdk-py