made reduce_along_dim preserve dtype by default (as discussed in #92)
Major NVector updates: defaults to row, allows any dtype, orientation
now controlled by shape rather than a property.
NVector#to_a for list, yale. Also added #each_stored_with_index (no
spec), which is needed for list and yale #shuffle and #shuffle!, also
included in this commit (with a spec).

Added create_vector function in spec helper file.
renamed dim method parameters to dimen to avoid NMatrix#dim naming confusion; added explicit call-seq blocks to mapping/reduction methods
Doc note about nd_row function needing work
Added #yale_nd_row_size. Improved #yale_a, #yale_ija, #yale_d by
allowing fetching of a single array value instead of the whole array.
Attempted to fix bug where yale matrices being multiplied may have
dissimilar dtypes (especially from the result).
Merge v0dro's #98, hopefully fixing #70
Merge branch 'master' of git://github.com/SciRuby/nmatrix into nmatrix-reduce-type-fixes

Conflicts:
	lib/nmatrix/nmatrix.rb
Fixed #99 sorting problem following Yale multiplication. Switched from
selection sort to quicksort/insertion sort. Improved spec for NVector
dot NVector so that it tests not only multiplication but also quicksort
and insertion sort.
Added leakcheck script and Rake task. Changed calloc call to ALLOC_N.
Fixed memory leak: storage was being freed, but matrix struct itself was
not! Also occurring in slicing. Oops.
Fixed get_slice leak (slice was sometimes being destroyed, but
components of slice struct were not). Fixed inconsistency where list
took care of freeing insertion values but yale and dense did not.
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
NMatrix::read now refuses to read a file that does not exist. Raises an
exception instead.
Merge branch 'master' of github.com:SciRuby/nmatrix
Fixed definition of abs on complex, added real_abs, imag_abs,
piecewise_abs.
Exposed cblas asum, not tested yet
Added/exposed BLAS::cblas_nrm2, convenience functions BLAS::nrm2 and
BLAS::anum. No tests written still. Also simplified code for complex
asum calculations.