0.5.0

• Major refactoring and rewrite of the library
• Units are now independent from dimensions
• Dimensions now depend on units (base or coherent units are provided in a class template)
• Quantity gets a Dimension template parameter again (as unit does not provide information about
  its dimension anymore)
• Spaceship operator support added
• Added official CGS system support
• Added official data information system support
• Repository file tree cleanup
• ratio refactored to contain Exp template parameter (thanks a lot @oschonrock!)
• SI fundamental constants added
• q_ prefix applied to all the UDLs (thanks @kwikius)
• unknown_unit renamed to unknown_coherent_unit
• Project documentation greatly extended and switched to Sphinx
• A few more usage examples added
• ASCII-only output support added (thanks @yasamoka)
• Representation values formatting extended (thanks @rbrugo)
• Output streams formatting support added
• Linear algebra from std::experimental::math support added
• Named SI units and their dimensions added (thanks @rbrugo
• libfmt updated to 6.2.0
• Added absolute functions and epsilon to math.h (thanks @mikeford3)
• Added a lot of prefixes to named units and introduced alias_unit (thanks @yasamoka)
• Linking with Conan targets only when they exists (#98)
• All physical dimensions and units put into physical namespace
• CMake improvements
• Velocity renamed to speed

Many thanks to GitHub users @oschonrock, @kwikius, and @i-ky for their support in drafting a new library design.