Add Jaeger exporter (open-telemetry#174)

This adds a Jeager exporter for OpenTelemetry.  This exporter is based
on https://github.com/census-instrumentation/opencensus-python/tree/master/contrib/opencensus-ext-jaeger.

The exporter uses thrift and can be configured to send data to the agent and
also to a remote collector.

There is a long discussion going on about how to include generated files
in the repo, so for now just put them here.

.flake8

@@ -1,2 +1,3 @@
 [flake8]
 ignore = E501,W503,E203
+exclude = .svn,CVS,.bzr,.hg,.git,__pycache__,.tox,ext/opentelemetry-ext-jaeger/src/opentelemetry/ext/jaeger/gen/,ext/opentelemetry-ext-jaeger/build/*

.isort.cfg

@@ -12,3 +12,4 @@ line_length=79
 ; )
 ; docs: https://github.com/timothycrosley/isort#multi-line-output-modes
 multi_line_output=3
+skip_glob=ext/opentelemetry-ext-jaeger/src/opentelemetry/ext/jaeger/gen/*

.pylintrc

@@ -7,7 +7,7 @@ extension-pkg-whitelist=
 
 # Add files or directories to the blacklist. They should be base names, not
 # paths.
-ignore=CVS
+ignore=CVS,gen
 
 # Add files or directories matching the regex patterns to the blacklist. The
 # regex matches against base names, not paths.

tox.ini

@@ -2,8 +2,8 @@
 skipsdist = True
 skip_missing_interpreters = True
 envlist =
-    py3{4,5,6,7,8}-test-{api,sdk,example-app,ext-wsgi,ext-http-requests}
-    pypy3-test-{api,sdk,example-app,ext-wsgi,ext-http-requests}
+    py3{4,5,6,7,8}-test-{api,sdk,example-app,ext-wsgi,ext-http-requests,ext-jaeger}
+    pypy3-test-{api,sdk,example-app,ext-wsgi,ext-http-requests,ext-jaeger}
     lint
     py37-{mypy,mypyinstalled}
     docs
@@ -23,6 +23,7 @@ changedir =
   test-api: opentelemetry-api/tests
   test-sdk: opentelemetry-sdk/tests
   test-ext-http-requests: ext/opentelemetry-ext-http-requests/tests
+  test-ext-jaeger: ext/opentelemetry-ext-jaeger/tests
   test-ext-wsgi: ext/opentelemetry-ext-wsgi/tests
   test-example-app: examples/opentelemetry-example-app/tests
 
@@ -38,6 +39,8 @@ commands_pre =
   ext: pip install {toxinidir}/opentelemetry-api
   wsgi: pip install {toxinidir}/ext/opentelemetry-ext-wsgi
   http-requests: pip install {toxinidir}/ext/opentelemetry-ext-http-requests
+  jaeger: pip install {toxinidir}/opentelemetry-sdk
+  jaeger: pip install {toxinidir}/ext/opentelemetry-ext-jaeger
 
 ; Using file:// here because otherwise tox invokes just "pip install
 ; opentelemetry-api", leading to an error
@@ -68,6 +71,7 @@ commands_pre =
   pip install -e {toxinidir}/opentelemetry-sdk
   pip install -e {toxinidir}/ext/opentelemetry-ext-azure-monitor
   pip install -e {toxinidir}/ext/opentelemetry-ext-http-requests
+  pip install -e {toxinidir}/ext/opentelemetry-ext-jaeger
   pip install -e {toxinidir}/ext/opentelemetry-ext-wsgi
   pip install -e {toxinidir}/examples/opentelemetry-example-app
 
@@ -84,6 +88,8 @@ commands =
          ext/opentelemetry-ext-azure-monitor/tests/ \
          ext/opentelemetry-ext-http-requests/src/ \
          ext/opentelemetry-ext-http-requests/tests/ \
+         ext/opentelemetry-ext-jaeger/src/opentelemetry \
+         ext/opentelemetry-ext-jaeger/tests/ \
          ext/opentelemetry-ext-wsgi/tests/ \
          examples/opentelemetry-example-app/src/opentelemetry_example_app/ \
          examples/opentelemetry-example-app/tests/