Update various bookshelf repositories.

steveklabnik · steveklabnik · commit 537eb45b9d8f · 2017-04-13T18:15:40.000-04:00
The book and the reference have both had changes lately; this integrates
them upstream.
diff --git a/src/doc/book b/src/doc/book
@@ -1 +1 @@
-Subproject commit a2c56870d4dc589237102cc5e0fe7b9ebd0d14a1
+Subproject commit beea82b9230cd641dd1ca263cf31025ace4aebb5
diff --git a/src/doc/reference b/src/doc/reference
@@ -1 +1 @@
-Subproject commit acedc32cacae80cf2f4925753a4ce7f7ffd7c86a
+Subproject commit b060f732145f2fa16df84c74e511df08a3a47c5d
