Added support for python-2.6
Use mode(1)

Otherwise all that fancy double-symbol modes are just not visible.
Started adding tests

Tests are temporary disabled on all branches except tests (does not really work
though, needs travis.yml in all branches).
Added tests.lib module with `replace_*()` with statement functions

Note: there is new problem: now multiprocessing() globals got assigned None
values. It is likely somehow related to extended `sys.modules` utilization
Omit using sys.modules if possible

Does not work though: still TypeError due to some global in multiproccessing
that got None
Added support for with: statement to tests.vim

Also made everything use new vim_module._with where possible
Made tests support python2.6

Old unittest is not working for unknown reason, using unittest2 instead