TAP runner does not work for 'omit' and 'pend'

Hi, I noticed that TAP runner does not work for 'omit' and 'pend'.

```ruby
# test.rb
require 'test-unit'
require 'test/unit/runner/tap'

class TestExample < Test::Unit::TestCase
  def test_omit
    omit
  end

  def test_pend
    pend
  end
end
```

Current behavior:

```
% ruby test.rb --runner=tap
1..2
# Finished in 0.000615406 seconds.
# 0 tests, 0 assertions, 0 failures, 0 errors, 0 pendings, 1 omissions, 0 notifications
```

After applying patch:

```
% ruby test.rb --runner=tap
1..2
not ok 1 - test_omit(TestExample)  # SKIP
# SKIP (Test::Unit::Omission)
# omitted.
# test.rb:7
#    5 class TestExample < Test::Unit::TestCase
#    6   def test_omit
# => 7     omit
#    8   end
#    9
not ok 2 - test_pend(TestExample)  # TODO
# TODO (Test::Unit::Pending)
# pended.
# test.rb:11
#     9
#    10   def test_pend
# => 11     pend
#    12   end
#    13 end
# Finished in 0.001272773 seconds.
# 2 tests, 0 assertions, 0 failures, 0 errors, 1 pendings, 1 omissions, 0 notifications
```