Release v2.0

This includes a bug fix that is a breaking change, so this is a new
major version.

Signed-off-by: Daniel Magliola <danielmagliola@gocardless.com>

CHANGELOG.md

@@ -0,0 +1,27 @@
+# CHANGELOG
+
+# 2.0.0 / 2020-01-28
+
+## Breaking changes
+
+- [#176](https://github.com/prometheus/client_ruby/pull/176) BUGFIX: Values observed at 
+    the upper limit of a histogram bucket are now counted in that bucket, not the following
+    one. This is unlikely to break functionality and you probably don't need to make code
+    changes, but it may break tests.
+
+## New features
+
+- [#156](https://github.com/prometheus/client_ruby/pull/156) Added `init_label_set` method,
+    which allows declaration of time series on app startup, starting at 0.
+
+
+# 1.0.0 / 2019-11-04
+
+## Breaking changes
+
+- This release saw a number of breaking changes to better comply with latest best practices
+  for naming and client behaviour. Please refer to [UPGRADING.md](UPGRADING.md) for details
+  if upgrading from `<= 0.9`.
+
+- The main feature of this release was adding support for multi-process environments such
+  as pre-fork servers (Unicorn, Puma).

lib/prometheus/client/version.rb

@@ -2,6 +2,6 @@
 
 module Prometheus
   module Client
-    VERSION = '1.0.0'
+    VERSION = '2.0.0'
   end
 end