Implements the given-when-then-based indentation

When enabled through feature-align-steps-after-first-word, it will align
steps *after* the first word, not before
Merge pull request #45 from deets/step-align-after-given-when-then

Implements the given-when-then-based indentation
fixing bug that would make first step fail to indent. Also, allow empty lines in steps.
Merge pull request #46 from deets/step-align-after-given-when-then

fixing bug that would make first step fail to indent. Also, allow empty ...