update docstring
relax some tests done with random data
Update licenses to GPL v3+ for all OpenCL kernels.

All contributors agreed on the licensing.
Related to #139
Update licenses to GPL v3+ for Cython module ...

clean up the code as well
Related to #139
Marching squares is under BSD (new). Agreed with Almar Klein
Update exactly the text of the license
#139
Large commit which updates all licenses for all Cython files and 
__init__.py.
related to #139
Update license of all tests
closes #139
Allow importing matplotlib without PyQt or PySide.
Closes #142 
At least I hope so :/
Merge remote-tracking branch 'origin/master'
related to #142
Very preliminar "prespective" work on
#144.

Nothing harmful for now ... but it may come later
related to #145
The cryptic GCC error message (inconsistent operand constraints in an
‘asm’)
refers to the fact that in PIC mode (which is activated by the
hardening
flags), %ebx is a reserved register.


related to bug #146
Some more reading about it:
https://lists.fedoraproject.org/pipermail/devel/2013-September/189137.html
factorize the cl kernel concatenation

this way this concatenation is done only in one place in the utils module
related to 149
related to #151
Manual for "detector2nexus"
related to #148
Correct docstrings for spelling
#147
Partial implementation
Related to #135