Update document
Update force_constants.py

FC are now calculated not basing on the inverse displacement (matrix), multiplied by the force matrix. Instead, for every force-displacement tensor elements the force-displacement linear regression fit is computed. It is done in the simplified zero-interception algorithm, thus calculations are fast. Additionally, the fitting error is calculated.
Merge branch 'patch-1' of https://github.com/lebecki/phonopy into merge-patch-1
Implement option to switch fc fitting algorithms
Minor change
Update force_constants.py

The code is much better problem-protected. Standard deviation cannot be computed if the number of elements is one, the variance can be negative and very small (numerical zero), and so on.
Merge patch-2 from KL
Fix minor bug
Option to extract scattering event class of imaginary part of self energy in spectrum plot
copy method
get_primitive_frame is rename to get_primitive_matrix in Primitive class; get_supercell_matrix is implemented in Supercell matrix.
Minor change
Creation of supercell is not relying on get_supercell in cells.py, which also allows to use 9 elements supercell matrix.
Update example
spglib update
Minor update of spglib
Let parse_BORN receive symmetry tolerance