Ignore files with a score of zero

[villfa]

When running Churn on a folder containing only one non-versioned PHP file (while the folder is part of a versioned project) we got this error:

    ___  _   _  __  __  ____  _  _     ____  _   _  ____
   / __)( )_( )(  )(  )(  _ \( \( )___(  _ \( )_( )(  _ \
  ( (__  ) _ (  )(__)(  )   / )  ((___))___/ ) _ (  )___/
   \___)(_) (_)(______)(_)\_)(_)\_)   (__)  (_) (_)(__)

    1 [->--------------------------] < 1 sec 4.0 MiB


In Assert.php line 2042:

  [InvalidArgumentException]
  Expected a value greater than 0. Got: 0


Exception trace:
  at vendor/webmozart/assert/src/Assert.php:2042
 Webmozart\Assert\Assert::reportInvalidArgument() at vendor/webmozart/assert/src/Assert.php:838
 Webmozart\Assert\Assert::greaterThan() at src/Result/Result.php:115
 Churn\Result\Result->getScore() at src/Result/ResultAccumulator.php:95
 Churn\Result\ResultAccumulator->toArray() at src/Command/RunCommand.php:185
 Churn\Command\RunCommand->writeResult() at src/Command/RunCommand.php:101
 Churn\Command\RunCommand->execute() at vendor/symfony/console/Command/Command.php:255
 Symfony\Component\Console\Command\Command->run() at vendor/symfony/console/Application.php:1009
 Symfony\Component\Console\Application->doRunCommand() at vendor/symfony/console/Application.php:273
 Symfony\Component\Console\Application->doRun() at vendor/symfony/console/Application.php:149
 Symfony\Component\Console\Application->run() at bin/churn:18

run [-c|--configuration [CONFIGURATION]] [--format FORMAT] [-o|--output OUTPUT] [-p|--progress] [--] [<paths>...]

[codecov]

Codecov Report

Merging #261 (4d23375) into master (4c1110e) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master     #261      +/-   ##
============================================
+ Coverage     95.92%   95.94%   +0.01%     
- Complexity      175      176       +1     
============================================
  Files            24       24              
  Lines           442      444       +2     
============================================
+ Hits            424      426       +2     
  Misses           18       18              

Impacted Files	Coverage Δ	Complexity Δ
src/Result/ResultAccumulator.php	100.00% <100.00%> (ø)	13.00 <0.00> (+1.00)

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