Add Loop Unrolling

Unroll only small loops whose bounds are statically known, as c++
compilers fail to understand the meaning of a plain list.
Add several examples gathered at scipy2013
Use a local loop iterator when translating list comprehension

This prevents some extra copies.
More accurate constness specification for iterators
Fix bad module naming when using custom output

When using the -o flag to give another name to a `.so', the generated
module was still using the input name internally, which is incorrect.

It now names the static module after the name given in the -o.
Fix bug in itertools product size computation.
Update README: Debian boost package is called libboost-dev
Update MANUAL: Debian boost package is called libboost-dev
Use perfect forwarding to prevent some copies

Less copies means better performances!
Fix PEP8 testing

An early exception prevented the test suite to be run normally...
Vectorized and Parallel version of numpy.sum

* Note that BOOST_SIMD_NO_STRICT_ALIASING is set to 1 to prevent a gcc bug
* Parallel reduction for non-scalar types is non supported yet.