Install libmemcached from source in all cases

See 
https://travis-ci.community/t/unable-to-load-dynamic-library-memcached-so/2232/9

Author: BanzaiMan

bin/compile-extension-memcached

@@ -4,17 +4,13 @@ set -o errexit
 source $(dirname $0)/compile-extensions-common
 
 function install_memcache() {
-	if [[ $(lsb_release -cs) = 'precise' || $(lsb_release -cs) = 'trusty' ]]; then
-		pushd /tmp
-		wget https://launchpad.net/libmemcached/1.0/1.0.18/+download/libmemcached-1.0.18.tar.gz
-		tar xzf libmemcached-1.0.18.tar.gz
-		pushd libmemcached-1.0.18
-		./configure --prefix=$INSTALL_DEST/$VERSION && make && make install
-		popd
-		popd
-	else
-		sudo apt-get install memcached
-	fi
+	pushd /tmp
+	wget https://launchpad.net/libmemcached/1.0/1.0.18/+download/libmemcached-1.0.18.tar.gz
+	tar xzf libmemcached-1.0.18.tar.gz
+	pushd libmemcached-1.0.18
+	./configure --prefix=$INSTALL_DEST/$VERSION && make && make install
+	popd
+	popd
 }
 
 travis_time_start