0.15.0

Full Changelog

• BREAKING! Remove do_transaction() function.
  It is literally a function receiving a function and calling it in the scope
  with transaction
• BREAKING! Rename default_context::transaction
  to default_context::default_transaction
transaction _; won't longer be ambiguous when both ureact
  and ureact::default_context namespaces are used
• #121 Add transaction::finish() to finish transaction before code scope is
  ended
• #127 Get rid of ureact_amalgamated.hpp
  It was used for godbolt example only, but now µReact is added on godbolt, so
  there is no longer reason to have it
• Allow calling zip with a single argument
• Add zip_transform adaptor
• Add enumerate adaptor
• Add adjustment and pairwise adapters of all possible flavors:
  • adjacent
  • adjacent_filter
  • adjacent_transform
  • pairwise
  • pairwise_filter
  • pairwise_transform
• #111 Add associative containers support in collect adaptor
• #122 Support iterators as observer's argument
• #123 Make sure transactions can't be started or finished when turn is in
  progress
• Fix member_ by making their copy/move constructors/assignments private