changed required precision for float64, complex128 lapack getrf to 1e-15.  Fixes #101.
Merge pull request #102 from cjfuller/lapack-spec-precision-fix

lapack getrf precision fix
Merge branch 'master' of https://github.com/SciRuby/nmatrix
NMatrix::read now refuses to read a file that does not exist. Raises an
exception instead.
Merge branch 'master' of github.com:SciRuby/nmatrix
Merge branch 'master' of https://github.com/SciRuby/nmatrix