Support 'key in bloom' in Python wrapper.

This is a more Pythonic usage than bloom.check(key), normally
implemented via a __contains__ method for a class written in
Python, but here via the sq_contains slot in the C code. Note
this implementation Only looks for strings (anything else
returns False).
new_counting_bloom_from_scale: don't take and fill in id and count

when mapping to an existing file, we don't get access to those
numbers until after new_counting_bloom_from_scale() calls bitmap_resize()

this went unnoticed for so long because the os mmaps the file a page
at a time, so it almost always maps a bit more of the file than was
requested
reduce error tightening ratio to 0.5

necessary for scaling bloom's false-positive rate to not increase
well beyond the desired error rate when multiple levels are full
Merge pull request #53 from ploxiln/tightening_ratio

reduce error tightening ratio to 0.499
version bump to 0.9.0, soname to 1.1

make all bindings match the main dablooms library version, for simplicity

the dynamic library was added after the most recent tagged version,
so it doesn't technically need a bump, but that seems like a long
time ago, and before the disk_seqnum thing, so I want to rev it
Merge pull request #54 from ploxiln/version_090

version bump to 0.9.0, bindings to 0.1
Merge pull request #50 from peterjc/py_contains

Support 'key in bloom' in Python wrapper.
tweak some Makefile variable names to be more conventional

rename:
PREFIX -> prefix
LIBDIR -> libdir
INCDIR -> includedir

refactor CFLAGS and LDFLAGS to better work with user preferences:
ALL_CFLAGS and ALL_LDFLAGS for flags that are probably required
replace LDLIBS with ALL_LDFLAGS
SHARED_LDFLAGS for building the shared library
use ALL_CFLAGS everywhere CC is used, including for linking
test tweaks: separate failures from warnings, exit with error if any failures
Merge pull request #56 from ploxiln/makefile_conventions

Makefile tweaks to match some conventions
offset should be type long, not int
Merge pull request #55 from lilydjwg/master

Use type long for offset