Implement comments

lib/ahem/lexer.rb

 class Lexer
   def initialize(source)
-    @source = source.split("\n").join(' ')
+    @source = source
     @position = 0
   end
 
   def get_token
     skip_whitespace
+    skip_comment
 
     return Token.new(TokenKinds::EOF) if at_end
 
     end
   end
 
+  def skip_comment
+    if @source.slice(@position..@position + 1) == '//'
+      @position += 2
+      @position += 1 until @source[@position] == "\n" || at_end
+      @position += 1 unless at_end
+    end
+  end
+
   def at_end
     @position == @source.size
   end

spec/lexer_spec.rb

       ]
     )
   end
+
+  it 'ignores comments' do
+    expect(Lexer.new("// prints 5\nprint(5)").scan_all).to eq(
+      [
+        Token.new(TokenKinds::IDENTIFIER, 'print'),
+        Token.new(TokenKinds::LPAREN),
+        Token.new(TokenKinds::NUMBER, 5),
+        Token.new(TokenKinds::RPAREN),
+        Token.new(TokenKinds::EOF),
+      ]
+    )
+  end
 end