v0.9.0

This release contains the start of the preparations needed for bringing Cachex to a v1.0.0.

As of this release, Cachex is being used in production systems (and safely).

Although the number of changes looks rather small, this release consists of quite a large delta (hence the bump to v0.9.0), many of them pertaining to interface design and structure, but also with several new feature additions:

• Added inspect/2 to inspect various components of the cache from an external process. Note that this is only the initial implementation and will be expanded before v1.0.0.
• Added execute/3 and transaction/3 to allow bulk execution of commands.
• Added the ability to control the timeouts for GenServer calls in the Cachex interface.
• Ensured that exists?/3 calls are counted in the Stats hook. Stats will be revisited before v1.0.0.
• Expanded the Cachex interface to accept a Worker instance. This is experimental and mainly to lay groundwork for v1.0.0.
• Optimised away overheads when opening too many transaction handles.
• Removed some messy macros from the Cachex interface. This leads to more readable code.