v0.7.5

What's Changed

• 49 support 4bit encodings by @noamteyssier in #50
• 48 move vbq index into file by @noamteyssier in #51
• 47 allow optional headers in vbq files by @noamteyssier in #52
• 53 convert vbq index cumulative records to u64 by @noamteyssier in #54
• 55 update documentation for new vbq formatting by @noamteyssier in #56
• 57 make per record flags optional by @noamteyssier in #58
• Binseq v2 by @noamteyssier in #60

Full Changelog: v0.6.5...v0.7.5