Fix deprecated uses of Redis#pipelined (#150)

Context: redis/redis-rb#1059

The following is deprecated
```ruby
redis.pipelined do
  redis.get(key)
end
```

And should be rewritten as:
```ruby
redis.pipelined do |pipeline|
  pipeline.get(key)
end
```

Functionally it makes no difference.
This API is available since Redis 3.0.

Co-authored-by: Jean Boussier <jean.boussier@gmail.com>

lib/stoplight/data_store/redis.rb

@@ -25,9 +25,9 @@ def names
       end
 
       def get_all(light)
-        failures, state = @redis.multi do
-          query_failures(light)
-          @redis.hget(states_key, light.name)
+        failures, state = @redis.multi do |transaction|
+          query_failures(light, transaction: transaction)
+          transaction.hget(states_key, light.name)
         end
 
         [
@@ -41,18 +41,18 @@ def get_failures(light)
       end
 
       def record_failure(light, failure)
-        size, = @redis.multi do
-          @redis.lpush(failures_key(light), failure.to_json)
-          @redis.ltrim(failures_key(light), 0, light.threshold - 1)
+        size, = @redis.multi do |transaction|
+          transaction.lpush(failures_key(light), failure.to_json)
+          transaction.ltrim(failures_key(light), 0, light.threshold - 1)
         end
 
         size
       end
 
       def clear_failures(light)
-        failures, = @redis.multi do
-          query_failures(light)
-          @redis.del(failures_key(light))
+        failures, = @redis.multi do |transaction|
+          query_failures(light, transaction: transaction)
+          transaction.del(failures_key(light))
         end
 
         normalize_failures(failures, light.error_notifier)
@@ -68,18 +68,18 @@ def set_state(light, state)
       end
 
       def clear_state(light)
-        state, = @redis.multi do
-          query_state(light)
-          @redis.hdel(states_key, light.name)
+        state, = @redis.multi do |transaction|
+          query_state(light, transaction: transaction)
+          transaction.hdel(states_key, light.name)
         end
 
         normalize_state(state)
       end
 
       private
 
-      def query_failures(light)
-        @redis.lrange(failures_key(light), 0, -1)
+      def query_failures(light, transaction: @redis)
+        transaction.lrange(failures_key(light), 0, -1)
       end
 
       def normalize_failures(failures, error_notifier)
@@ -91,8 +91,8 @@ def normalize_failures(failures, error_notifier)
         end
       end
 
-      def query_state(light)
-        @redis.hget(states_key, light.name)
+      def query_state(light, transaction: @redis)
+        transaction.hget(states_key, light.name)
       end
 
       def normalize_state(state)