v1.3.1

Fixed typo in `readme.md`.

v1.3.0

• Fixed a bug where errors thrown from performLockedOperation would cause a 'lock leak'!

v1.2.0

• Added Semaphore#performLockedOperation(callback)
• Fixed a bug wherein semaphores were not properly waiting for an available lock slot.

v1.0.0

Removed straggling `console.log` statements.