0.7.0

Great headers rework. µReact is not longer single-header library

• "include/ureact/ureact.hpp" is separated into several more specialized headers.
  "single_include/ureact/ureact_amalgamated.hpp" contains all the headers content,
  but has no CMake target. Its main purpose is to be used in godbolt snippets.
• std::invoke() is used instead of functional call in most of the places receiving
  func or predicate, so member access and member function calls can be performed.

struct User
{
    int age;
    int get_age(){ return age; }
};

ureact::context ctx;
auto user = make_var( ctx, User{18});
auto user_age = lift( user, &User::age );
assert( user_age.get() == 18 );
auto user_age_2 = lift( user, &User::get_age );
assert( user_age_2.get() == 18 );

• ureact::lift() overloads have optional first template parameter to select
  desired type of resulting signal
• default signal type deduction for ureact::lift() removes references from
  the invoke result type
• ureact::reactive_ptr() and ureact::reactive_ref() are merged into new
  ureact::reactive_ref() that works as both
• curried version of ureact::flatten() is added
• unary version of ureact::lift() is optimized to steal op from temp_signal<S>&&
  sources like unary signal operators did.
  unary signal operators are reworked to call unary ureact::lift() with standard
  unary functors when it is possible (std::negate<> and others)
• binary version of ureact::lift() is added in form ureact::lift(lhs, op, rhs).
  It is optimized to steal op from temp_signal<S>&& sources like binary signal
  operators did.
  binary signal operators are reworked to call binary ureact::lift() with standard
  binary functors when it is possible (std::plus<> and others)
• -Wimplicit-int-float-conversion suppression is removed from lift code
• additional sanity assert in temp_signal::steal_op() is added
• curried version of ureact::observe() is added
• new ureact::tap() algorithm is added. It works like ureact::observe(),
  but returns received source instead of observer

see the full changelog