Add classes chapter

Author: paulgoetze

2_Classes/1_Your_first_class/solution.rb

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+class Programmer
+end

2_Classes/1_Your_first_class/solution_spec.rb

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+require 'rspec'
+
+[['solution::code']]
+
+describe 'Your code' do
+  it "defines a class Programmer" do
+    expect(Object.const_defined?('Programmer')).to be true
+  end
+
+  if Object.const_defined?('Programmer')
+    describe Programmer do
+      it "allows instantiating a new Programmer" do
+        expect { Programmer.new }.not_to raise_error
+      end
+
+      it "defines a Programmer class without any methods" do
+        expect(Programmer.public_instance_methods(false)).to be_empty
+        expect(Programmer.singleton_methods(false)).to be_empty
+        expect(subject.protected_methods(false)).to be_empty
+        expect(subject.private_methods(false)).to be_empty
+      end
+    end
+
+  end
+end

2_Classes/1_Your_first_class/task.md

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+# Your first class
+
+You can define a class with the *class* keyword followed by the
+camelcased name of the class.
+Keep in mind to close the class definition with the *end* keyword, e.g.:
+
+`class ClassName`
+`end`
+
+Camelcasing the class name is not necessary, but is a naming convention in Ruby.
+
+---
+
+Define a class *Programmer* similar to the example above!
+
+---