Add tests to the tests/hooks.test.js + tests/git-manager.test.js file - mocha

[kazazor]

Test cases - tests/hooks.test.js:

1. all of the pre-commit hook files are being copied as planned
2. all of the pre-commit hook files are added with the permission to execute (chmod 755)
3. existing pre-commit hook is being deleted when installing the package

Test cases - tests/git-manager.test.js:

1. Check that initializing the singleton instance sets the right git root directory

Using:

1. gulp-mocha
2. Write the tests using mocha