Refactoring of tests. Introduce Travis CI & Codecov.io

[jodator]

This PR:

• introduces StorageRepository for managing many storage json files
• adds basic IoC for passing: history, rank and aliases
• adds more tests
• adds Travis CI setup for testing on different node versions
• adds codecov.io setup for code coverage visualisation

[jodator]

@pjasiun: You'll need to create Travis CI & codecov.io accounts (authorize them) to be able to see them in action:

• https://travis-ci.org/pjasiun/fuma
• https://codecov.io/gh/pjasiun/fuma

Only login & authorize both Travis & Codecove - then all should be done automatically. as here:

• https://travis-ci.org/jodator/fuma
• https://codecov.io/gh/jodator/fuma

[jodator]

Codecov.io for branch: https://codecov.io/gh/jodator/fuma/branch/t%2F30