fix shortOptionCapturesValue fails getting 0 or '0'

[fcamp]

Adds a safer emtpy check in GetoptParser::shortOptionCapturesValue

[harikt]

Looks we need to fix the Travis config and installation of phpunit to fix issues. Interested in looking into it ?

[fcamp]

@harikt I noticed that tests use an old version of phpunit. Updating them won't be too much work.

However ContainerTest is based on a class outside the repository

[harikt]

Do you want to make any changes to the container test? If not composer will manage dependencies