Updated code sample suggestion for 'To Map, or Not to Map'

- Using an Ordering type class instead of extending Ordered
- 'collection map { ... }' style instead of 'collection.map(...)'
- replaced 'straight' foreach with a version that appears more equivalent to the confusing version
Merge pull request #95 from scalapuzzlers/tweak-13

Updated code sample suggestion for 'To Map, or Not to Map'