v0.10: cista::bitset, improved cista::tuple

What's Changed

• add bitset container by @felixguendling in #114
• Fix pretty printers by @julianharbarth in #119
• bitset pretty printer by @felixguendling in #120
• add byte_buf to memory_holder variant by @pablohoch in #122
• fix popcnt for win32 msvc by @felixguendling in #124
• New tuple by @julianharbarth in #127
• make variant ctor constexpr by @felixguendling in #125

Full Changelog: v0.9...v0.10