Nested tests with labels and completion durations

[monadius]

Fixes #3.

Nested tests with labels are supported as test groups (DESCRIBE).

Example kumite: https://www.codewars.com/kumite/620a7361d746e5000f36a021/

Test output:

<IT::>Top level test case

<FAILED::>not equal

<COMPLETEDIN::>0.17

<DESCRIBE::>Test Odd

<IT::>Should return false for 1

<PASSED::>Test passed

<COMPLETEDIN::>0.73

<IT::>Should return false for 7

<PASSED::>Test passed

<COMPLETEDIN::>0.57

<COMPLETEDIN::>1.43

<DESCRIBE::>Test even

<IT::>Should return true for 100

<PASSED::>Test passed

<COMPLETEDIN::>1.43

<IT::>Should return true for 42

<PASSED::>Test passed

<COMPLETEDIN::>1.42

<COMPLETEDIN::>3.50

<DESCRIBE::>Test edge cases

<DESCRIBE::>Test zero

<IT::>Should return true for 0

<PASSED::>Test passed

<COMPLETEDIN::>0.65

<COMPLETEDIN::>0.72

<DESCRIBE::>Test -1

<IT::>Should return false for -1

<PASSED::>Test passed

<COMPLETEDIN::>1.21

<COMPLETEDIN::>1.29

<COMPLETEDIN::>2.04

<DESCRIBE::>Unlabeled tests

<IT::>

<FAILED::>Incorrect answer for n=100<:LF:>not equal

<COMPLETEDIN::>1.98

<IT::>

<FAILED::>Incorrect answer for n=100<:LF:>not equal

<COMPLETEDIN::>1.99

<DESCRIBE::>

<IT::>

<FAILED::>Incorrect answer for n=100<:LF:>not equal

<COMPLETEDIN::>1.31

<IT::>

<FAILED::>Incorrect answer for n=100<:LF:>not equal

<COMPLETEDIN::>1.13

<COMPLETEDIN::>2.68

<COMPLETEDIN::>6.76

<DESCRIBE::>Nested labels

<DESCRIBE::>Outer label

<DESCRIBE::>Inner label

<DESCRIBE::>Tests with nested labels

<IT::>

<FAILED::>Incorrect answer for n=100<:LF:>expected: false but got: true

<COMPLETEDIN::>2.06

<IT::>

<FAILED::>Incorrect answer for n=100<:LF:>expected: false but got: true

<COMPLETEDIN::>1.29

<COMPLETEDIN::>3.55

<COMPLETEDIN::>3.56

<COMPLETEDIN::>3.56

<COMPLETEDIN::>3.57