v6.7.0

• Removed numpy dependency
• word_segmentation now retains/preserves case.
• word_segmentation now keeps punctuation or apostrophe adjacent to previous word.
• word_segmentation now normalizes ligatures: "scientific" -> "scientific".
• word_segmentation now removes hyphens prior to word segmentation (untested).
• American English word forms added to dictionary in addition to British English e.g. favourable & favorable.