all applied migrations on initial migration are new

on the initial run, there are no previous entries. this pr sets
newEntries to match all applied entries in this case, which
fixes gh-2

lib/command/apply.ts

@@ -54,7 +54,7 @@ export default function apply(config: Config) {
 
   let previousEntry = journal.then(es => R.last(es));
   let newEntries = Promise.join(previousEntry, apply, (prev, es) =>
-    R.filter(e => e.timestamp > prev.timestamp, es)
+    prev ? R.filter(e => e.timestamp > prev.timestamp, es) : apply
   );
 
   return newEntries