feat(collect!): collected! and tests implemented

[ddrkt]

No description provided.

[RobolabGs2]

1. There are usually first - expected value, second - actual in asserts.
2. Standard matrix shows a different behavior:

irb(main):001:0> require 'matrix'
=> true
irb(main):002:0> m = Matrix[[1, 2], [3, 4]]
=> Matrix[[1, 2], [3, 4]]
irb(main):003:0> m.collect{ |e| e.join(',') }
Traceback (most recent call last):
       15: from C:/Ruby26-x64/bin/irb.cmd:31:in `<main>'
       14: from C:/Ruby26-x64/bin/irb.cmd:31:in `load'
       13: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
       12: from (irb):3
       11: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:472:in `collect'
       10: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:491:in `collect!'
        9: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:583:in `each_with_index'
        8: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:583:in `each_with_index'
        7: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:583:in `each'
        6: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:584:in `block in each_with_index'
        5: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:584:in `each_with_index'
        4: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:584:in `each'
        3: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:585:in `block (2 levels) in each_with_index'
        2: from C:/Ruby26-x64/lib/ruby/2.6.0/matrix.rb:491:in `block in collect!'
        1: from (irb):3:in `block in irb_binding'
NoMethodError (undefined method `join' for 1:Integer)
irb(main):004:0> m.collect{ |e| e+1 }
=> Matrix[[2, 3], [4, 5]]

[RobolabGs2]

It would be nice if you make also parameter witch such as in standard.

collect(which = :all)
Returns a matrix that is the result of iteration of the given block over all elements of the matrix. Elements can be restricted by passing an argument:
:all (default): yields all elements
:diagonal: yields only elements on the diagonal
:off_diagonal: yields all elements except on the diagonal
:lower: yields only elements on or below the diagonal
:strict_lower: yields only elements below the diagonal
:strict_upper: yields only elements above the diagonal
:upper: yields only elements on or above the diagonal