Xrayutilities

* new materials (Cr, tetragonal BaTiO3)
* fix bug in DarwinModel
* fix multiprocessing on MS Windows platforms
* fix BUG in tetragonal crystals (wrong symmetry was used!)

* fix of negative HKL directions in RelaxationTriangle
* new SGLattice class which replaces Lattice and allows for easier material
definitions
* old Lattice class is still included but now deprecated and will be removed
in >1.5.0
* new PowderExperiment, PowderDiffraction and PowderModel classes for proper
simulation of powder patterns. Thanks to Marcus Mendenhall for his
contribution of a Fundamentals parameter approach powder profile
calculation.
* cache database results -> huge speedups in repeated calls with same
parameters
* new file parser for ILL numor files (station D23, maybe more general)
* add possibility to fix the pixel size when calibrating 2D detectors
* new normalized Lorentzian function (NormLorentz1d)
* add fully asymmetric Pseudovoigt (different width and eta)
* remove unphysical variation of structure factor in kinematical 2-beam model
* new dynamical multibeam simulations based on the Darwin theory of dynamical
diffraction
* include pip install guide into readme
* fix default wavelength selection in line cut functions.

* fix packaging of the README.md file

* call PowderIntensity from xu.Powder init routine
* fix problems in Crystal class when no lattice base is defined
* add parsing for simply chemical formulas in Amorphous definitions
* fix setup.py issue related to test installation
* fix bug in fuzzy gridders (first data point was not always treated correct!)
* added absorption_length method in all material classes

* fix windows build due to lack of support of C99 in MSVC

* change to setuptools for installation/package building
* major code cleanup (remove of duplicated code using Clone Digger)
http://clonedigger.sourceforge.net
* bug fixes in Alloy initialization
* documentation building now requires numpydoc
* central version number in VERSION file (also available in the package after
importing: import xrayutilities as xu; xu.__version__
* new examples using the new XRR and XRD simulation-code
* improve handling of SiGe and AlGaAs alloy: alloying on atomic level
* add relaxation parameter to PseudomoprhicMaterial to model partially relaxed
material
* fix fwhm_exp for very narrow peaks
* fitting of x-ray reflectivity using the lmfit package.
If you want to use this new feature you have to install lmfit
see https://pypi.python.org/pypi/lmfit/
* new subpackage simpack for diffraction and reflectivity simulations from
thin film samples. So far implemented are
- a basic kinematical diffraction model
- two dynamical diffraction models (simplified and general 2-beam theory)
- a model for specular reflectivity calculations using a Parrat-like
formalism
* fwhm_exp function was moved to math's subpackage! This was necessary in
order to avoid circular dependencies, but anyhow the function also
fits better there!
* improvements of peak_fit function
- better ability to handle linear background
- more stable fitting due to use of deriavitives (PseudoVoigt)
* minor improvement in peak_fit's plotting