Implement V2 configuration loading (#557)

* Implement V2 configuration loading

Implemented reading of generic parts of V2 configuration from Viper and
validation of the configuration.

Added stretchr/testify library to be able to use helpers like assert() in tests.

Testing done: automated tests

* Fix PR comments

Author: tigrannajaryan

go.mod

@@ -44,6 +44,7 @@ require (
 	github.com/spf13/cobra v0.0.3
 	github.com/spf13/viper v1.2.1
 	github.com/streadway/quantile v0.0.0-20150917103942-b0c588724d25 // indirect
+	github.com/stretchr/testify v1.3.0
 	github.com/tinylib/msgp v1.1.0 // indirect
 	github.com/uber-go/atomic v1.3.2 // indirect
 	github.com/uber/jaeger-client-go v2.16.0+incompatible // indirect

go.sum

@@ -371,7 +371,6 @@ github.com/streadway/quantile v0.0.0-20150917103942-b0c588724d25 h1:7z3LSn867ex6
 github.com/streadway/quantile v0.0.0-20150917103942-b0c588724d25/go.mod h1:lbP8tGiBjZ5YWIc2fzuRpTaz0b/53vT6PEs3QuAWzuU=
 github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=