bumped version to 3.1.0

see 1f726f8104bc281412adaa2488bf74c425d291c6

Merge pull request #15 from euhmeuh/master

Update LICENSE.md

Throw an explicit exception when trying to subscribe a client interface that has return values

refactored code

refactored HubProxy.CreateSubscription(...)

refactored code, introduced csharp 6 features

improved subscriptions (using On<> instead of Subscribe)

added PublicAPI annotation

removed samples for Call(...) and Call<T>(...)

Removed Sync-Calls (see #8)

renamed HubProxyExtensions to SignalRExtensions

fixed searchpath of output files

added try..catch to stop buildprocess on error