AUTHORS and CITATION added

AUTHORS

+BornAgain source code is currently developed by
+
+* Dmitry Yurov
+* Gennady Pospelov
+* Joachim Wuttke
+* Jonathan Fisher
+* Marina Ganeva
+* Walter Van Herck
+
+Our former contributors:
+
+* Abhishek Khanna
+* Céline Durniak
+* David Li
+* Ivonna Li
+* Jan Burle
+* Mohammad Mahadi Hasan
+* Rebecca Brydon
+* Sezer Karaca

CITATION

+Citing BornAgain
+
+C. Durniak, M. Ganeva, G. Pospelov, W. Van Herck, J. Wuttke (2015)
+BornAgain — Software for simulating and fitting X-ray and neutron small-angle scattering
+at grazing incidence, version <...>, http://www.bornagainproject.org