Support tuple -> list conversion

Useful whenever tuples are not supported by pythran: just convert them
to a list (if it is meaningful). For instance to iterate over a tuple...
Huge rework of itertools

* indent everything properly
* use std::forward to avoid unnecessary copies
* do not store the value computed by the operator*

As a result, izip and imap are really faster (x2 on a bench here), I did
not implement the same optimizations for ifilter and generate. Yet.
Fix ExpandImport ordering

It should be called sooner, otherwise some analysis choke on an unknown
identifiers which turns out to be a name imported from a module.
Rework generator representation

Still not perfect, but at least does not lead to bugs in the validation.
Itertools corrections and optimizations.

* ifilter and product optimization (no more useless copy)
* using random_access iterators when possible, forward iterators otherwise
* itertools tests now use complex generator expressions
Merge pull request #50 from Nagadum/genex_transform

Itertools corrections and optimizations.
Update TODO with assigned task

So that everybody can know which tasks are already in progress.
Bugfix in map and ifilter :
* correct handling of generator expressions
* correct initialization of ifilter
* more tests to cover these cases
Merge pull request #51 from Nagadum/bugfix

Bugfix in map and ifilter :
Merge branch 'master' of github.com:serge-sans-paille/pythran
Make Python and Cxx backend denser

Remove additional newlines that were disgraceful in doc test strings.
Code cleaning

Use generic_visit whenever possible.
Improve Methods Normalization

* Now allows to call methods as a function, e.g. list.append(l,1)
* More testing too
Rework NormalizeAttribute pass

Now that NormalizeMethods is more complete, NormalizeAttribute is
getting simpler.
Clean up for cxxgen
Harmonize the __builtin__ module with other modules

ExpandBuiltins makes sure all builtins are referenced as members of the
__builin__ module.

This removes a lot of ugly hooks to handle intrinsics in a different way
than other modules.
Add a failfast mode to setup.py test

For easier debugging of failing test cases. Requested by Pierrick!
Code cleaning, commenting and refactoring

* More comments
* Less spaghetti code
* Cleaner implementation of intrinsic.py
Merge pull request #52 from pbrunet/master

Clean up for cxxgen.py
Rework pass manager interface

* Un-spaghettify class hierarchy
* rework API as a combination of `prepare' and run

`prepare' gathers analysis dependencies
`run' performs the transformation

to add more preparation, overload prepare
to add post-processing, overload run