Make iterable variables lazy
Add more unfolded types

* It could be folded with more analysis about size of output.
Add documentation for conversion and add more builtin folded type
Remove unused variable
Merge pull request #283 from pbrunet/more_lazy

More lazy
Add wpmvp14 papers in the master branch
Add iop2014 paper in the master
Add cpc2013 paper in the master
Add slices from PyHPC (sc2013)
Turn pow2 into numpy.square

Use existing numpy.square functions instead of the fake pow2 one.
Improve the implementation of numpy.square using nt2::sqr.

This fixes #292.
Merge pull request #293 from serge-sans-paille/pow2-to-square

Turn pow2 into numpy.square
Merge pull request #291 from pbrunet/papers

Papers
Add test annotation for test tuning

* Thanks to pytest mark, we can select tests with -m module (to execute
* only module annotate class) and -m not module (to execute only not
* annotate class)