Update README

README.md

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+FileCache is a file-based caching library for Ruby. It's 
+available for download from [RubyForge][rubyforge-filecache]
+
+# Note about the current code
+
+I haven't touched this code since I wrote it in 2008! I don't
+use Ruby much any more. I'm putting it on Github to make it easy
+for people to find, tweak and extend it. Please feel free to 
+drag it into the 21st century and send me pull requests.
+
+# Installation
+
+    gem install -r filecache
+
+(On a Unix-like system you'll probably want to run that with sudo.)
+
+# Synopsis
+
+```ruby
+require 'rubygems'
+require 'filecache'
+
+cache = FileCache.new
+cache.set(:key, "value")
+puts cache.get(:key)     # "value"
+cache.delete(:key)
+puts cache.get(:key)     # nil
+
+# create a new cache called "my-cache", rooted in /home/simon/caches
+# with an expiry time of 30 seconds, and a file hierarchy three 
+# directories deep
+cache = FileCache.new("my-cache", "/home/simon/caches", 30, 3)
+cache.put("joe", "bloggs")
+puts(cache.get("joe"))   # "bloggs"
+sleep 30
+puts(cache.get("joe"))   # nil
+```
+
+[rubyforge-filecache]: http://rubyforge.org/projects/filecache/