more documentation in README.org from array.lisp and interface.lisp

Signed-off-by: AJ Rossini <blindglobe@gmail.com>
documentation regarding the use of CARRAY, CVECTOR, and XSLICE

Signed-off-by: AJ Rossini <blindglobe@gmail.com>
minor doc fixes.

Signed-off-by: AJ Rossini <blindglobe@gmail.com>