allow all line-based nodes to have a comment attached to it
add test case to format scenario with step comments
implement formatting of scenario and step comments
add comment and blank line parsing to dom parser
remove whitespace directly within the peg-parser
updated gherkin.peg.go
start using goimports \o/
implement formatting/preserving of comments and blank lines (at least within scenarios)
remove test.feature as there are no tests validating it
add cmdline options for new formatter options
add version file along with build/install Makefile targets

also moved the gherkinfmt command into ./cmd/ subfolder