Change some more defaults with MongoDB

* Change logic to only use `replset` on production ... as per Automattic/mongoose#3588 (comment) from @chrisckchang
* Default to single connection on development with `server` ... as per Automattic/mongoose#3588 (comment) from @chrisckchang
* Change `connectTimeoutMS` to 60 seconds instead of presumed inherited OS value from https://github.com/christkv/mongodb-core/issues/66#issuecomment-165052045 by @christkv and overridden with @chrisckchang recommendation previously mentioned in commit summary.
* Added NOTE on non-standard keepAlive value that was in before I started twiddling with this... this was on dev and pro pre replica/sharding set.

Applies to OpenUserJS#845, OpenUserJS#851, OpenUserJS#852, Automattic/mongoose#3588 and loosely christkv/mongodb-core#66

Refs:
* Automattic/mongoose#3588 (comment)

app.js

@@ -46,33 +46,32 @@ var connectStr = process.env.CONNECT_STRING || settings.connect;
 var sessionSecret = process.env.SESSION_SECRET || settings.secret;
 var db = mongoose.connection;
 
-var dbOptions = {
- server: {
+var dbOptions = {};
+if (isPro) {
+ dbOptions.replset = {
  poolSize: 5,
  socketOptions: {
  autoReconnect: false,
  noDelay: true,
- keepAlive: 1,
- connectTimeoutMS: 0,
+ keepAlive: 1, // NOTE: Unclear why this was non-zero early on
+ connectTimeoutMS: 60 * 1000,
  socketTimeoutMS: 0
  },
  reconnectTries: 30,
  reconnectInterval: 1000
  }
-};
-
-if (isPro) {
- dbOptions.replset = {
+} else {
+ dbOptions.server = {
  secondaryAcceptableLatencyMS: 15,
  poolSize: 5,
  socketOptions: {
  noDelay: true,
  keepAlive: 0,
- connectTimeoutMS: 0,
+ connectTimeoutMS: 60 * 1000,
  socketTimeoutMS: 0
  }
  }
-};
+}
 
 var fs = require('fs');
 var http = require('http');