Add step to zip up all of the input data

Fixes #78
diff --git a/index.js b/index.js
index 72b367b..56e8c02 100644
--- a/index.js
+++ b/index.js
@@ -666,6 +666,10 @@
     overallProgress.beginTask('Downloading osm boundaries')
     asynclib.eachSeries(Object.keys(osmBoundarySources), downloadOsmBoundary, cb)
   }],
+  zipInputData: ['makeDistDir', 'getOsmBoundaries', function (results, cb) {
+    overallProgress.beginTask('Zipping up input data')
+    exec('zip dist/input-data.zip downloads/* timezones.json osmBoundarySources.json expectedZoneOverlaps.json', cb)
+  }],
   createZones: ['makeDistDir', 'getOsmBoundaries', function (results, cb) {
     overallProgress.beginTask('Creating timezone boundaries')
     asynclib.each(Object.keys(zoneCfg), makeTimezoneBoundary, cb)