Merge pull request JohnSundell#43 from JohnSundell/process-inject

Enable a custom Process instance to be injected

Merge pull request JohnSundell#23 from SteveBarnegren/dont_close_stan…

…dard_file_handlers

Don't close standard file handlers

Merge pull request JohnSundell#40 from hisaac/master

Update to Swift 4.2

Merge pull request JohnSundell#25 from harlanhaskins/on-your-mark-get…

…-set-go

Synchronize reads/writes to outputData and errorData

README: Recommend using HTTPS to add ShellOut to Marathon

Merge pull request JohnSundell#7 from JohnSundell/linux-fix

Fix build errors on Linux

README: Add instructions for pre-defined commands

README: Update for new series of commands + path API

Make ShellOutError members public