Changelog for concurrent-hashtable

Unreleased changes

0.1.8

• Changed insertIfExists to add.
• Added swapValues.
• Added readAssocsIO.
• Simplified STMAction.
• Improved documentation.
• Fixed bug in resize when initial table size is less than _numResizeWorkers.

0.1.7

• Added modify.
• Included StmContainers.Map in the benchmarks.
• Haddock updates.