Fast mode and first stars scanning

Features

• Add fast mode (enabled by default) (#17)
  • this mode ensures that if a repository contains more than (by default) 1000 stars, only 1000 random stargazers will be scanned among all
  • the fast mode can be disabled by adding --fast=false. The amount of stars to compute in fast mode can also be changed by using the -s or --stars option
  • this means that with the default value of 1000, scanning a big repository with thousands of stars takes about 25-30 minutes
• Add scanFirstStars mode (disabled by default) (#19)
  • allows scanning the first X stargazers of a repository. Useful for repositories which are now big but might have cheated at the beginning

Improvements

• Red color threshold moved from <25% to <50% (#21)

Bug fixes

• Percentiles are now computed as a part of the overall trust algorithm (#21)