Rework filter - first test
Update to main
Working proto of compiled filters
More bytearrays

Moved all internal arrays of bytes to bytearrays.
Results are still arrays, because it could be 16 bit
About ready compiled filters
Unimport script

small utility that conception of compiled filters based on
Update from main repo

Test are still broken (suppose because of not updated)
Fix filters

Which was broken due to move of methods
Rework adaptive filters

Move them into separate method.
Also tune some line filtering.

*pngfilters.py removed as it is only generated file which is equal to
'BaseFilter' class + unimport.py script (unlike pngfilters.c which
require Cython to build)
separate _process_XXXX method for each chunk type.
Do not do pyximport.install() (it's something an app might do,
not a library). See #23.
More care about bytearrays
More rework of adaptive filters

Now it can be tuned with users methods
Update tests

Add filter testing in 'Adam7write'
Add bitdepth 16 to 'RGBtoRGBA'
Bugs and style fixes
Rename 'len' function for override

To allow usage Python 'len' function in Cython
Bugfix for Python 2.4
Checked

That's correct.
No more 'psize' in Writer

Only planes and bitdepth,
pixel size moved to filter object.
cdef methods are private now

To simulate cython restriction in python version