Bump SD exporter to 0.7.1 for release (census-instrumentation#749)

fix typo (census-instrumentation#742)

v0.6.0 release

0.5.0 release (census-instrumentation#630)

New packages:
- opencensus-ext-azure 0.1.0

Minor version updates:
- opencensus 0.5.0
- opencensus-ext-django 0.3.0
- opencensus-ext-flask 0.3.0
- opencensus-ext-grpc 0.2.0
- opencensus-ext-ocagent 0.3.0
- opencensus-ext-pyramid 0.3.0
- opencensus-ext-stackdriver 0.3.0

Micro version updates:
- opencensus-ext-dbapi 0.1.2
- opencensus-ext-google-cloud-clientlibs 0.1.2
- opencensus-ext-httplib 0.1.2
- opencensus-ext-jaeger 0.2.1
- opencensus-ext-mysql 0.1.2
- opencensus-ext-postgresql 0.1.2
- opencensus-ext-prometheus 0.2.1
- opencensus-ext-pymongo 0.1.2
- opencensus-ext-pymysql 0.1.2
- opencensus-ext-requests 0.1.2
- opencensus-ext-sqlalchemy 0.1.2
- opencensus-ext-threading 0.1.2
- opencensus-ext-zipkin 0.2.1

v0.4.1 and stackdriver v0.2.1 release (census-instrumentation#615)

Prepare for 0.4.0 release (census-instrumentation#604)

Release opencensus-0.4.0 and multiple new versions of ext packages. This
release includes breaking changes related to the context API and stats/metrics
exporters. It also adds a dependency on the new opencensus-context package.

Merge branch 'v0.3.1-ext-release' into v0.3.x

Prepare for 0.3.0 release (census-instrumentation#554)

Prepare for 0.2.0 release

Bump version to 0.1.11

and add a changelog.