scattered::vector roadmap

[gnzlbg]

Functionality:

• enable move constructor only if exception safe
• enable constructors that take allocators?
• enable initializer lists?
• document member functions
• make sure doxygen documentation is nice
• fortify: assert preconditions in member functions
• cach template instantiations errors as soon as possible: e.g. static_assert
  that keys exist
• corner cases: static_assert empty structs?
• enable emplace_back?
• reasonable tests coverage
• user-defined comparison functor for floating point operations
• insert should take InputIt instead of const_iterator

Performance

• optimize relational operators
• improve insert (use the underlying container insert)

Testing:

• improve test struct: make template, use inheritance, add function pointers
  and arrays
• test more algorithms, rvalue references, exception safety, bit fields
• test using a std::vector instead of boost::container::vector
• test iterators and references extensively: reverse_iterator, const_iterator,
  const_reference, const_pointer.