v0.7.0

Added Features

• estd::tuple now can operate in sparse mode, meaning it can fold down to 0 size if all its members are also 0 size.
• Wrapping willemt's awesome bipbuffer as layer1::bipbuf and layer3::bipbuf
  • See https://www.codeproject.com/Articles/3479/The-Bip-Buffer-The-Circular-Buffer-with-a-Twist

Added Features (internal)

Early access - marked internal mainly due to naming and API flux, but passes tests:

• Added out_buffered_stringbuf and out_bipbuf_streambuf wrapper for "true" streambuf operations. These sit in front of a raw streambuf for additional caching.
• Core units capability - including bytes and percent and SI helpers for converting to string

Quality Updates & Bug Fixes

• Bringing back c_str() to layer1 and layer2 strings
• Various AVR and estd::variadic cleanup
• Fixed bug in to_chars (#28)