Added pollStreamForeverSafe variant which returns a Result to handle …

[Swoorup]

Fixes #2

…Redis polling exceptions.

For each streams (Akka, Hopac, Observable) adding a pollstreamForeverSafe variant which returns Result to handle polling specific exception and also allows to resume for where previously left off instead of terminating the stream.

Types of changes

What types of changes does your code introduce to FSharp.Control.Redis.Streams?

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• Build and tests pass locally
• I have added tests that prove my fix is effective or that my feature works (if appropriate)
• I have added necessary documentation (if appropriate)

[TheAngryByrd]

Looks good! Do you mind adding a few tests to make sure things work out?

• integration test hitting similar to this
• Test mocking the IDatabase StreamRangeAsync method and throwing an excetion and testing we got an error out of it