Bump pants to 0.0.15.  Bump upstream twitter.common dependencies to 0.1.1.

Testing Done:
Tested against the aurora repository -- required only one minor change:

ba=aurora=; git diff
diff --git a/BUILD b/BUILD
index eb2ff0d..509b4c6 100644
--- a/BUILD
+++ b/BUILD
@@ -1 +1,4 @@
 maven_layout()
+
+# allow python artifacts to be exported from src/main/thrift
+SourceRoot.register('src/main/thrift', PythonLibrary)

Which is surprising but good -- then again we're currently only using it for
the Python pipeline and there are fewer knobs there.

Reviewed at https://rbcommons.com/s/twitter/r/89/