Remove fibonacci and fix publicity for few structures for separating fibonacci example

[PayneJoe]

This PR has two modifications for the purpose of separating fibonacci example:

• Remove fibonacci example
• Fix publicity for few structures, eg, treepp and OP_HINT

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Files	Coverage Δ
src/lib.rs	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes