Bump dependencies for Laravel 10 (#44)

Add in composer reqs for Laravel v9 (#43)

Fix isFeatureEnabled returns false when multiple strategies are confi…

UserWithId Strategy calls id() method on User Model (#32)

Make endpoint and request options configurable. (#28)

Add Middleware feature.enabled, feature.disabled (#26)

Bind GuzzleHttpClient as default client for Unleash. (#29)

- Changes cache TTL default to 15s, the standard default
- Add unleash.cache.failover option that will pull the last successful result from the cache
  - This setting is independent of regular caching
  - The cache is always stored, to allow enabling the feature during a failure incidence
- This change also moves the requests for features out of the constructor
  - Possible to use in Facades
  - Still "cached" for the lifetime of the Unleash object

Allow passing variadic args into `Unleash->isFeatureEnabled()`/`Unlea…

Add Unleash and Feature facades (#24)