[DEM-NNN] fix qiskit dependency on 0.6.x

0.7.x has changed the backend infrastructure considerably, so
for now stick to 0.6.x while we refactor things to be compatible
with the new stuff.

setup.py

@@ -47,4 +47,4 @@ def get_version_number(module):
       packages=['quantuminspire', 'quantuminspire.qiskit', 'quantuminspire.projectq'],
       install_requires=['pytest>=3.3.1', 'coverage>=4.5.1',
                         'coreapi>=2.3.3', 'numpy', 'jupyter'],
-      extras_require={'qiskit': ["qiskit>=0.6.1"], 'projectq': ["projectq>=0.4"]})
+      extras_require={'qiskit': ["qiskit>=0.6.1, <0.7.0"], 'projectq': ["projectq>=0.4"]})

src/quantuminspire/version.py

@@ -1 +1 @@
-__version__ = '0.3.0'
+__version__ = '0.3.1'