Improve console output

When pretty fails, its output does not end on a new line, displaying something like this:
```
ngdo@ngdo-portable:~$ pretty fail/
Unrecognized command 'fail/'
Available commands:
- pretty: runs an analysis (will not fix the code)
- pretty fix: fix as many errors as possible in the code
- pretty ci: runs an analysis in a continuous integration environment
- pretty help: displays this helpngdo@ngdo-portable:~$ 
```

This fix add an empty line to display this:
```
ngdo@ngdo-portable:~$ pretty fail/
Unrecognized command 'fail/'
Available commands:
- pretty: runs an analysis (will not fix the code)
- pretty fix: fix as many errors as possible in the code
- pretty ci: runs an analysis in a continuous integration environment
- pretty help: displays this help
ngdo@ngdo-portable:~$ 
```

pretty

@@ -94,6 +94,7 @@ function assertPhpCodeSnifferIsInstalled($command)
         echo <<<INSTRUCTIONS
 ERROR: PHP CodeSniffer does not seem to be installed because the '$command' program cannot be found.
 You can install it by following the instructions here: https://github.com/squizlabs/PHP_CodeSniffer#installation
+
 INSTRUCTIONS;
         exit(1);
     }
@@ -105,6 +106,7 @@ function assertPhpCsFixerIsInstalled()
         echo <<<'INSTRUCTIONS'
 ERROR: PHP-CS-Fixer does not seem to be installed because the 'php-cs-fixer' program cannot be found.
 You can install it by following the instructions here: https://github.com/FriendsOfPHP/PHP-CS-Fixer#installation
+
 INSTRUCTIONS;
         exit(1);
     }
@@ -118,5 +120,6 @@ Available commands:
 - pretty fix: fix as many errors as possible in the code
 - pretty ci: runs an analysis in a continuous integration environment
 - pretty help: displays this help
+
 HELP;
 }