Use debhelper to install bitcoind.bash-completion

contrib/debian/bitcoind.bash-completion

@@ -0,0 +1 @@
+contrib/bitcoind.bash-completion	bitcoind

contrib/debian/control

@@ -5,6 +5,7 @@ Maintainer: Jonas Smedegaard <dr@jones.dk>
 Uploaders: Micah Anderson <micah@debian.org>
 Build-Depends: debhelper,
  devscripts,
+ bash-completion,
  libboost-system-dev (>> 1.35) | libboost-system1.35-dev,
  libdb4.8++-dev,
  libssl-dev,

contrib/debian/rules

@@ -9,7 +9,7 @@ DEB_INSTALL_EXAMPLES_bitcoind += debian/examples/*
 DEB_INSTALL_MANPAGES_bitcoind += debian/manpages/*
 
 %:
-	dh $@
+	dh --with bash-completion $@
 
 override_dh_auto_build:
 	cd src; $(MAKE) -f makefile.unix bitcoind