Cleaning up the api.

Sources/Models/Sensor.swift

@@ -0,0 +1,15 @@
+
+/// Represents a sensor that provides a reading.
+public struct Sensor<Reading>: Equatable {
+  
+  /// The topic to retrieve the reading from.
+  public var topic: String
+  
+  /// Create a new sensor for the given topic.
+  ///
+  /// - Parameters:
+  ///   - topic: The topic to retrieve the readings from.
+  public init(topic: String) {
+    self.topic = topic
+  }
+}