Work for week 3

[cvvergara]

Please for this week start working on the following:

• [x] You need to create an include/metrics/centrailty.hpp similar to this one
• [x] Of course delete what is not needed (aka, floydWarshal or Jonhson you choose) and start coding for centrality code from boost.
• [x] Rename/adjust what ever you need to rename/adjust on that file.
• [x] Use here that include file, so that it gets compiled.
• [x] try to solve as many compilation errors you can.
• [x] Next monday we will do the compilation together and try to fix any remaining issues about compilation.