check binary version instead of using which to check if binary is present, fixes #59
fix spec for failing to resolve bin
fix using version in checking if bin is accessible
don’t fail when converting nil to String if pngout was not found
silence stderr when getting version for bins which output version to stdout
check for jpegrescan presence as it has no version
fail if getting version for bin was not defined
raise allowed cyclomatic complexity to 10
Merge branch 'avoid-which'