improve reputation calculations

[stojanov-igor]

Improve the current calculations based on the research and design.

The calculations should be implemented based on design document that is provided here: #36

[stojanov-igor]

Intermediate Reputation calculation

After each task, the user can provide a rating on a scale of 1 to 5. For each rating, we increase the reputation of the profile as shown below.

New Reputation = Old Reputation + Weight of current evaluation

Rating = Reputation weight
1 = -2
2 = -1
3 = 0
4 = +1
5 = +2

[stojanov-igor]

Found another paper that we can use for later implementation: https://link.springer.com/content/pdf/10.1007/978-3-642-10383-4_42.pdf .

For now the solution above should suffice.