abby 0.2.0

The library is now mainly an adaptation of the AABBCC library.

Changes

• Added tree::clear
• Added tree::height
• Added tree::rebuild
• Added tree::print
• Change behaviour of tree::insert to take a lower and upper bound vector.
• Remove tree::emplace
• Rename: tree::query_collisions -> tree::query
• Rename: tree::replace -> tree::update
• Further minor tree member functions that were are result of porting the AABBCC version.