Allow read flags definition from remote server

[matheuslc]

Problem

At this time we only can read the flags from a file inside the application.

How to solve?

In some way, allows reading from a remote server that can be a CDN or another remote file system service.

For what this can be used?

• Removes from us the need to create a new commit for add or remove a flag.
• Allow us to read from a remote feature flag service and the "Feature Flagger" operates like a gem client.

Suggestion

Add Strategy concept to handle another type of reading flags definition. We can have one strategy to a local file system and another to a remote file system.