Remove magic string from test collection specification

Merge development branch for v5.6.0

(intellisense correction)

Readme - add note for twitter notification (App-vNext#339)

Escape symbols in nuspec (App-vNext#291)

Add interface providing read-only access to a policy registry (App-vN…

…ext#283)

* Add interface providing read-only access to a policy registry

Adds an interface providing read-only access to a policy registry. Useful to prevent consumers changing policies in registry; for example to enforce separation of population of policy registry from usage.

* Add IReadOnlyPolicyRegistrySpecs

Merge pull request App-vNext#263 from reisenberger/v5.2.0

Add PolicyRegistry and interfaces to Polly (v5.2.0)

Merge pull request App-vNext#244 from reisenberger/reisenberger/featu…

…re/expandcontextusage

v5.1.0: Allow different parts of an execution to exchange state through `Context` flowing with execution

Update NetStandard.Library dependency to NETStandard.Library 1.6.1. (A…

…pp-vNext#229)

Update NetStandard.Library dependency to NETStandard.Library 1.6.1, to
resolve compatibility for some Xamarin targets.

Fixes App-vNext#228

Merge pull request App-vNext#225 from reisenberger/v505doco-NoOpPolicy