Add --no-progress option to differentiate between progress bars output

[maks-rafalko]

This PR:

• Adds new option --no-progress to differentiate between progress bars output. The name is not related to progress bars only, it will be used for any CI-related things.
• Covered by tests
• Doc updated

Fixes #613

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From #613

Another option is to use something like the DotFormatter instead of the progress bars.

Current implementation saves the number of files/mutations generated in strings, which gives more useful information for developer (as well as with debugging for maintainers) rather than dots.

Before:

After:

❗️ We can also implement Travis autodetection to enable new loggers automatically even if --ci-friendly is not passed by developer. WDYT?

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This change is 

[sanmai]

Travis and CI autodetection is the way it should work. It is as simple as checking for presence of any two below environment variables:

CI=true
CONTINUOUS_INTEGRATION=true

[sanmai]

What do you think about renaming this option into --no-progress? This way it will be obvious exactly what it does, and it is a common standard option for other tools. E.g. composer has it.

[maks-rafalko]

• Renamed to --no-progress (however, I still think --ci-friendly may be useful if we are going to extend its meaning not for progress bars only, but i'm ok with --no-progress)
• Added CI autodetection

[sanmai]

Looks good.

[maks-rafalko]

Thanks @sanmai for the review

[sanmai]

No problem, please ask me anytime if there's a need for a second set of eyes.