Fixes invariant so interval (a:c) gets added to js.
a
  \
    \
      \
       d
      /
    c
   /
 b
Allows users to try to remove intervals not in the collection. Stops as soon as it possitively knows that it is not in the collection.
Document reference equality on IBS AVL
Adds small contract and comment to IBS AVL
Removes old todos that proved not to be achievable.
Removes some parameter names that weren't being used.
Tests that removing an interval in a collection returns true, whereas removing it again returns false.
Adds method for building tree structure from endpoints. At the moment still commented out, so we can benchmark it later.
Merge branch 'master' of https://github.com/lundmikkel/C5