Remove the index from the test case loop; simplify the cases object - #887

Summarized changes:
```
» g diff | grep '^[+-][^+-]' | sort | uniq -c
      1 +        "cases": cases,
      1 -        "cases": list(enumerate(cases)),
     90 +{% for case in cases %}
     90 -{% for idx, case in cases %}
      1 -{%- if idx == 0 %}
     60 -    {% if idx == 0 %}# {% endif %}[[ $BATS_RUN_SKIPPED == "true" ]] || skip
     28 -  {% if idx == 0 %}# {% endif %}[[ $BATS_RUN_SKIPPED == "true" ]] || skip
      1 +{%- if loop.first %}
     60 +    {% if loop.first %}# {% endif %}[[ $BATS_RUN_SKIPPED == "true" ]] || skip
     28 +  {% if loop.first %}# {% endif %}[[ $BATS_RUN_SKIPPED == "true" ]] || skip
```