Merge pull request #64 from Eyescale/master

Make blas detection more robust
Fixed compilation problem regarding std::min and std::max
Fixed memory problem in matrix.hpp
Added get_sub_tensor4 to tensor4
Added init_hosvd to t4_hooi
Added quantize_log to tensor4
Added stdev, variance, mean, min, max, abs_min and abs_max to tensor4
Added an ALS without the core as a parameter to t4_hooi
Added missing return type
Improved tensor3 and tensor4's frobenius_norm methods
Enable CI testing