closes#423
If the parsed JSON data curled during a bash installation is not valid, use the repository's tag files
as a backup. If those files don't exist somehow, then checkout the master branch and install it.
This new feature can be accessed by invoking rustlings with --nocapture.
Both unit and integration tests added.
closes#262
BREAKING CHANGES:
The following function take a new boolean argument:
* `run`
* `verify`
* `test`
* `compile_and_test`