理由はわかりませんが、コンソール出力は次のとおりです。
undefined method `model' for main:Object
/Users/Jerome/Desktop/UrbanImpact/config/application.rb:3:in `<top (required)>'
/Users/Jerome/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/Users/Jerome/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
/Users/Jerome/Desktop/UrbanImpact/Rakefile:4:in `<top (required)>'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/rake_module.rb:25:in `load'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/rake_module.rb:25:in `load_rakefile'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:501:in `raw_load_rakefile'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:82:in `block in load_rakefile'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:81:in `load_rakefile'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:65:in `block in run'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/gems/rake-0.9.2.2/bin/rake:33:in `<top (required)>'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/bin/rake:19:in `load'
/Users/Jerome/.rvm/gems/ruby-1.9.2-p290/bin/rake:19:in `<main>'
これは、「rails server」と入力するとコンソールに表示されます
どんな助けでも大歓迎です！