Remove map_test.*
Add catch.hpp
Let Catch define main()
Add test.cpp
Delete libnstd/map.cpp
Add method definitions to libnstd/map.h
Fix parameter types for map::insert()
Revert "Fix parameter types for map::insert()"

This reverts commit b681fe63f9b8b2a946993351d1da53f77c4ab042.
Implement map::insert()
Cosmetic changes
Add map::Node::operator*()
Implement map::iterator::operator->()
Increment map::size on insert()
Cosmetic changes
Implement map::find()
Fully implement map::insert()