Add version 0.3.0+1 to changelog

Author: Fox32

CHANGELOG.md

@@ -1,6 +1,6 @@
 ## 0.1.0
 
-- Initial version
+- Initial version.
 - Implements `Counter`, `Gauge` and `Histogram`. 
 - Includes a shelf handler to export metrics and a shelf middleware to measure performance.
 
@@ -10,4 +10,8 @@
 
 ## 0.3.0
 
-- Implement `Summary` metric type
+- Implement `Summary` metric type.
+
+## 0.3.0+1
+
+- Increase version constraint range on package `collection` to `^1.14.11` to be compatible with flutter.