Update version number, add changelog (census-instrumentation#463)

Author: c24t

CHANGELOG.md

@@ -0,0 +1,18 @@
+# Changelog
+
+## Unreleased
+
+## 0.2.0
+Released 2018-01-18
+
+- Fix multiple stackdriver and prometheus exporter bugs
+- Increase size of trace batches and change transport behavior on exit
+  ([#452](https://github.com/census-instrumentation/opencensus-python/pull/452))
+
+## 0.1.11
+Released 2018-01-16
+
+- Fix a bug in the stackdriver exporter that caused spans to be exported
+  individually
+  ([#425](https://github.com/census-instrumentation/opencensus-python/pull/425))
+- Add this changelog

opencensus/__version__.py

@@ -12,4 +12,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__version__ = '0.1.8'
+__version__ = '0.2.dev0'