Log Message:
py-numexpr: update to 2.6.3

Changes from 2.6.2 to 2.6.3
- Documentation now available at readthedocs.io_.
- Support for floor() and ceil() functions added by Caleb P. Burns.
- NumPy requirement increased from 1.6 to 1.7 due to changes in iterator
  flags.
- Sphinx autodocs support added for documentation on readthedocs.org.
- Fixed a bug where complex constants would return an error, fixing
  problems with `sympy` when using NumExpr as a backend.
- Fix for 277 whereby arrays of shape (1,...) would be reduced as
  if they were full reduction. Behavoir now matches that of NumPy.
- String literals are automatically encoded into 'ascii' bytes for
  convience.