Restore forward-bias for timespan parsing

This broke as a result of updating the Chrono version in e1b7b1b.
It’s too bad because it wasn’t a major version change! Other
parsing bugs remain but it addresses this one:
#68 (comment)

app/utils/parse-timespan.js

@@ -44,7 +44,7 @@ chronoInstance.refiners.push(assumePM);
 
 export default function parseTimespan(value) {
   const [parsed] = chronoInstance.parse(value, new Date(), {
-    forwardDatesOnly: true,
+    forwardDate: true,
   });
   return parsed;
 }

tests/unit/utils/parse-timespan-test.js

@@ -72,4 +72,23 @@ module('Unit | Utility | parse timespan', function(hooks) {
     );
     assert.notOk(parsed.end);
   });
+
+  test('it assumes future dates unless fully specified', function(assert) {
+    window.chronokinesis.travel(new Date(1570925744254));
+    // Saturday 2019-10-12 19:15
+
+    assertParsing(
+      assert,
+      'thursday from 7 to 9',
+      '2019-10-17 19:00',
+      '2019-10-17 21:00'
+    );
+
+    assertParsing(
+      assert,
+      'oct 10 2019 from 1 to 4',
+      '2019-10-10 13:00',
+      '2019-10-10 16:00'
+    );
+  });
 });