Add slides for L1
Merge branch 'master' of github.com:UCL-RITS/research-computing-with-cpp

* 'master' of github.com:UCL-RITS/research-computing-with-cpp:
  Update README.md
Added headings for next 4 pages
Merge branch 'master' of https://github.com/UCL-RITS/research-computing-with-cpp into lecture-1

* 'master' of https://github.com/UCL-RITS/research-computing-with-cpp:
  Add slides for L1
Up to unit testing