changes for #62 and #64,
support for 4+ dimensional nfft in nfftmex,
add error handling to nfftmex init_guru,
faster generic nfft in nfft.c,
semi-explicit 4d and 5d nfft in nfft.c,
matlab/octave tests for 4d and 5d nfft,
automatic precomputations in nfft.m class
changes for #62 and #64, support for 4+ dimensional nfft in nfftmex, add error handling to nfftmex init_guru, faster generic nfft in nfft.c, semi-explicit 4d and 5d nfft in nfft.c, matlab/octave tests for 4d and 5d nfft, automatic precomputations in nfft.m class