Added additional *indgen shortcuts and changed behavior for some;
now, #cindgen for :complex64, #zindgen for :complex128, #findgen
for :float32, #dindgen for :float64, #rindgen for :rational128,
and #rbindgen for Ruby objects (which contain integers); also,
removed code repetition
Merge branch 'master' of github.com:SciRuby/nmatrix
Updated history for @cjfuller's improvements, including fixes to #152
and #153