Clarify/simplify implementation of Fenwick Tree

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Remove trailing whitespace in README file

.travis.yml: remove version printing of GCC and CMake

.travis.yml: remove redundant comment

.travis.yml: use bionic distro to get more compliant GCC by default

.travis.yml: paralellize make

.travis.yml: remove redundant version printings

.travis.yml: use default Ubuntu dist (currently xenial)

.travis.yml: allow any branch

Number theory - basics module - minor tweaks

Extended euclid tweaks (#98)

Added missing some missing headers

ceil_div, floor_div refactor. (#96)

Matrix refactor (#95)