Fix typo in runShellCommand method

Signed-off-by: Aaron Kuzemchak <aaron@kuzemchak.net>
Fix 'UnexpectedValueException' when using hierarchical namespace
Merge pull request #411 from piccagliani/Fix_UnexpectedValueException

'UnexpectedValueException' occurs when using hierarchical namespace
fix to attachFile doc
Merge pull request #394 from akuzemchak/393

Fix typo in runShellCommand method
Merge branch 'master' of git://github.com/Codeception/Codeception