Added example 311 for learning migrations.
Removed Ex0311 from model names, use symbols instead of strings for table and column names, added sku column to Item.
Started new Rails app at 312.
Added answer to 309 as 312.
Added new Rails app at 315.
Added Sinatra restaurant app at 313.
Converted restaurant app from 313 to Rails app in 315.
Merge branch 'master' into GN