Add StringKeyedUnorderedMap to Makefile

Test Plan:
unit tests

Reviewed By: bwatling@fb.com

Subscribers: stepan, folly-diffs@, yfeldblum, trunkagent, vikas, alikhtarov

FB internal diff: D1890511

Tasks: 6311387

Signature: t1:1890511:1425924980:71af7c12a09a86b280dc3c9a9ef0756bf56bf639

folly/Makefile.am

@@ -79,6 +79,9 @@ nobase_follyinclude_HEADERS = \
 	experimental/SharedMutex.h \
 	experimental/Singleton.h \
 	experimental/Singleton-inl.h \
+	experimental/StringKeyedCommon.h
+	experimental/StringKeyedUnorderedMap.h \
+	experimental/StringKeyedUnorderedSet.h \
 	experimental/TestUtil.h \
 	FBString.h \
 	FBVector.h \