Add missing include in Token.hh
WIP: PipelineParser
WIP: PipelineParser
WIP: PipelineParserTest: constructor
WIP: PipelineParserTest: failing token parser
WIP: PipelineParserTest: non-keyword token, single command
WIP: PipelineParserTest: keyword token, single command
WIP: PipelineParserTest: negated single command
WIP: PipelineParserTest: negated three commands