Rewrite tests/example-test.cpp to use addressbook example from capnproto C++ project.

tests/addressbook.capnp

@@ -0,0 +1,58 @@
+# From https://github.com/sandstorm-io/capnproto/blob/6816634a08b08bc8f52b4ee809afb58389f19655/c%2B%2B/samples/addressbook.capnp
+#
+# Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+# Licensed under the MIT License:
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+@0x9eb32e19f86ee174;
+
+using C = import "/c.capnp";
+$C.fieldgetset;
+
+struct Person {
+  id @0 :UInt32;
+  name @1 :Text;
+  email @2 :Text;
+  phones @3 :List(PhoneNumber);
+
+  struct PhoneNumber {
+    number @0 :Text;
+    type @1 :Type;
+
+    enum Type {
+      mobile @0;
+      home @1;
+      work @2;
+    }
+  }
+
+  employment :union {
+    unemployed @4 :Void;
+    employer @5 :Text;
+    school @6 :Text;
+    selfEmployed @7 :Void;
+    # We assume that a person is only one of these.
+  }
+}
+
+struct AddressBook {
+  people @0 :List(Person);
+}
+