added readme

Author: stephens2424

readme.md

@@ -0,0 +1,20 @@
+# RRule
+
+[![GoDoc](https://godoc.org/github.com/stephens2424/rrule?status.svg)](https://godoc.org/github.com/stephens2424/rrule)
+
+Package RRule implements recurrence processing according to RFC 5545. See the
+[godoc](https://godoc.org/github.com/stephens2424/rrule) for usage information.
+
+This implementation was written to overcome performance issues in previous
+implementations. Those previous ones were generally implemented as direct
+translations of the venerable python-dateutil, however the algorithms were
+complicated and probably didn't use Go's language features effectively enough
+for performance optimization. The observed problem was particularly acute under
+GopherJS.
+
+The library here is essentially complete. A fair number of various patterns are
+tested, particularly simple ones. The library has not seen, at the time of this
+writing, any production usage, however. Issue reports with implementation
+accuracy or performance problems are particularly welcome.
+
+Licensed under BSD-3. See the LICENSE file.