Migration sql changes (#199)

* safe migration script changes

* lamassu migration script fixes

migrations/1509091634946-support_logs.js

@@ -2,11 +2,11 @@ var db = require('./db')
 
 exports.up = function (next) {
   const sql =
-    [`create table support_logs (
+    [`create table if not exists support_logs (
     id uuid PRIMARY KEY,
     device_id text,
     timestamp timestamptz not null default now() )`,
-    'alter table logs add column server_timestamp timestamptz not null default now() '
+    db.addColumn('logs', 'server_timestamp', 'timestamptz not null default now()')
     ]
 
   db.multi(sql, next)