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.
Merge branch 'master' of github.com:serge-sans-paille/pythran
change std::array to core::array to have a conversion constructor

* a = ((1,2), (3.5, 4.5)) didn't work
Fix len for tuple

* tuple doesn't have iterator type
Fix zip with different size iterator

* we tested the end of the first iterator in zip but the reference
  is the shortest iterator
add comparison between list and empty list
improve string interface

* negative index (only for const acces as no other access can happen from user on strings)
* fix slices
* print for string_view
* slices of string_view
* boolean test for string_view
Fix imap

* iterable were saved to avoid dangling references but it was not this values
  which was passed to others constructors. Now, iterable are saved in imap_iterator
   and it works. More perfect forwarding are enabled BUT iterable are saved twice:
   in begin() AND in end() of _imap