Fixes #25 unit files dependencies

unit-files/mysql-importer@.service

 [Unit]
 Description=MySQL importer
+
+# Dependency ordering
 Before=mysql@%i.service
 
+# Dependency binding
+BindsTo=mysql@%i.service
+
 [Service]
 Type=oneshot
 RemainAfterExit=yes

unit-files/nginx-discovery@.service

@@ -3,7 +3,6 @@ Description=%p for %i etcd registration
 
 # Requirements
 Requires=etcd.service
-Requires=nginx@%i.service
 
 # Dependency ordering
 After=etcd.service

unit-files/nginx-importer@.service

@@ -4,6 +4,9 @@ Description=nginx importer
 # Dependency ordering
 Before=nginx@%i.service
 
+# Dependency binding
+BindsTo=mysql@%i.service
+
 [Service]
 Type=oneshot
 RemainAfterExit=yes

unit-files/wordpress-discovery@.service

@@ -3,7 +3,6 @@ Description=%p for %i etcd registration
 
 # Requirements
 Requires=etcd.service
-Requires=wordpress@%i.service
 
 # Dependency ordering
 After=etcd.service

unit-files/wordpress-importer@.service

@@ -5,6 +5,9 @@ Description=WordPress importer
 After=mysql-importer@%i.service
 Before=wordpress@%i.service
 
+# Dependency binding
+BindsTo=wordpress@%i.service
+
 [Service]
 Type=oneshot
 RemainAfterExit=yes