Knex adapter & connection management

This release adds a Knex adapter, bringing SQL database support alongside Redis.
Connection handling has been improved: Redis now only closes connections it owns, making it safer to use shared/external connections. Adapter instances are now cached to avoid unnecessary re-instantiation.
On the performance side, pool filling now uses parallelized pop operations for faster job retrieval.

Commits

• feat(adapter): add knex adapter (c41fc8b)
• fix(manager): cache adapter instances (8cd76b8)
• feat(redis): only quit the connection when we own it (89cb921)
• docs(readme): add benchmark value with 100k jobs (45579d9)
• docs(readme): update benchmark results with real stuff (b998045)
• refactor(benchmark): allow to take duration as a params (df13753)
• refactor(worker): parallelize pop for filling the pool (15cdc86)

Full Changelog: v0.0.1-alpha.0...v0.0.1-alpha.1