README.md in total-0.2.0 vs README.md in total-0.3.0

@@ -20,9 +20,30 @@
 ```ruby
 require 'total'
 puts Total::Mem.new.bytes
 ```
 
+The following platforms are supported:
+
+  * MacOSX
+  * Linux
+  * FreeBSD
+  * <del>Windows</del> (help needed)
+
+If the platform is not recognized or is not supported, `Total::CantDetect` exception
+will be raised. You should catch it and proceed accordingly, for example:
+
+```ruby
+def total_mb
+  Total::Mem.new.bytes / (1024 * 1024)
+rescue Total::CantDetect
+  512
+end
+```
+
+This code will return the actual memory size in Mb, if it can be detected,
+or 512 otherwise.
+
 That's it.
 
 # How to contribute
 
 Read [these guidelines](https://www.yegor256.com/2014/04/15/github-guidelines.html).