Make test_nil_is_an_object pass

  * gave assert_equal the value 'true' on line 5

  * this should match the return value for nil.is_a?(Object)

[#75305758]
Make test_nil_has_a_few_methods_defined_on_it test pass

  * set assert_equal argument to NoMethodError on line 16, confirmed in irb

  * used the first part of error message 'undefined method' to fix line
  * 20

[#75305758]
Make test_nil_has_a_few_methods_defined_on_it test pass

  * set the appropiate arguement values for lines 25 to 27

[#75305758]