Code need minor update to work with latest version of Swift

[rayx]

FYI. I made the following change to RWMRuleScheduler.swift to build it on my system:

--- RWMRuleScheduler_old.swift      2019-12-07 22:09:57.000000000 +0800
+++ RWMRuleScheduler.swift      2019-12-07 22:54:54.000000000 +0800
@@ -467 +467 @@
-                            let weeksInYear = lastWeek == 1 ? CountableRange(weeksRange).last! : lastWeek
+                            let weeksInYear = lastWeek == 1 ? weeksRange.last! : lastWeek
@@ -495 +495 @@
-                                if let date = calendar.date(fromRelative: comps) {
+                                if let date = calendar.date(from: comps) {
@@ -541 +541 @@
-                                            days = Array(CountableRange(range).indices)
+                                            days = Array(range.indices)

The issues with the original code are:

1. CountableRange is now an alias to Range. No need to convert any more.
2. Calendar.date() doesn't have fromRelative param.

BTW, I wasn't able to use the library successfully using cocoapods. The app I created was a command line app. I was able to install the library in my app using the workaround suggested by johnsusek in #1. But building my app failed with dyld: Library not loaded: Reason: image not found. Not sure why. So I actually copied RWMRecurrenceRule.swift, RWMRuleParser.swift, RWMRuleScheduler.swift, and test files to my project (I didn't try those EKEvent, EKRecurrenceRule, and Calendar extension files).