Improve BloomFilter efficiency.

Applies the patch from CASSANDRA-1220:

"[T]he table of false positives for a given number of bits per element and a given number of hashes in BloomCalculations is incomplete. This patch includes the calculations from Table 5 of Bloom Filters - The Math, which is referenced in the documentation at the source of the table. This changes the optimal number of hashes for the Bloom filters created by SSTableWriter (with 15 bits per element) from 8 to 10, with a reduction in the false positive rate from 0.000852 to 0.000744. (The patch also extends the table to include false positive rates for 16-20 bits per element for future reference.)"

https://issues.apache.org/jira/browse/CASSANDRA-1220
Remove unused import.
Merge pull request #4 from codahale/pr/CASSANDRA-1220

Improve BloomFilter efficiency
Fix handling of small cardinality cases in CountThenEstimate merges
Merge pull request #5 from jmeagher/small-merge-fix

Fix handling of small cardinality cases in CountThenEstimate merges
- add data for maven central
- config for Sonatype OSS repository
scm config
[maven-release-plugin] prepare release v2.1.1
[maven-release-plugin] prepare for next development iteration
Newer and less finiky version of the release plugin
( it actually releases)
Merge branch 'v2.1.x'

Conflicts:
	pom.xml
Count-Min Sketch datastructure for estimating frequencies (and other things, but currently just frequencies).
Added notice about frequency estimation / Count-Min Sketch to README
Expand * imports
Merge pull request #6 from jkff/count-min-sketch

Count min sketch
fixes #7

There were two problems.

1) Math.pow(2,32) == Math.pow(-2,32) in java, not good...
2) The long range correction algorithm reduces precision in some cases
so I've given the caller the option of disabling this function
fix typo
minor: meaningless comments
minor: formatting, docs.
Serializer seems unused and not very useful (can't imagine a case where it can't be replaced with a usage of ByteBuffer.putX, DataOutput or ObjectOutputStream)