Fixes def method_with_block -   
def test_methods_can_call_yield_many_times. I learned:

* A block in one method can be called in another. 

* A block can be called with both yield, do .. end and |arguments|.

* Methods can call yield many times.

[#65861868]
Fixes through the end of the file. I learned:

* if statement can be used to see if methods have been called with a block.

* block can modify and assign new value to an original object. Ex: 

value = :initial_value
method_with_block { value = :modified_in_a_block }
value == :modified_in_a_block 

* blocks can be assigned to variables and called explicitly. Ex: 

add_one = lambda { |n| n + 1 }
add_one.call(10) == 11

or 
add_one[10] == 11

* stand alone blocks can be passed to methods expecting blocks.

* methods with explicit blocks can can then take a block. Ex: 

def method_with_explicit_block(&block)
    block.call(10)
  end

method_with_explicit_block { |n| n * 2 } == 20


[#65851868]
Merge pull request #18 from kkburr/65851868_about_blocks_master

about blocks master

[Delivers #65851868]