Fixes #1739: (Workaround) Pin the version of reflection-docblock

[greg-1-anderson]

A new version of the reflection-docblock project was released, introducing strict syntax-checking on the @Usage tag. @Usage is not documented in the phpdocumentor documentation at the time of this writing. Presumably, this is a new addition.

This is a short-term fix to allow CI builds using Terminus to work again.

Longer-term fixes:

1. Perhaps the Terminus installer should fetch the Terminus composer.lock file and then install via composer install, so that the tested dependencies are always used. Installing via composer create-project also respects composer.lock files.

2. The annotated command library should probably use a bespoke docblock comment parser to avoid problems with changing definitions of the parent library

[greg-1-anderson]

Short-term recommendation: Assuming tests pass, merge this and tag a stable release so that CI scripts will start working again.

[coveralls]

Coverage remained the same at 94.199% when pulling 2522c6b on pin-reflection-docblock into deb495a on master.

[arosboro]

This change fixes my CI build. I changed line 46 of circle.yml to cgr "pantheon-systems/terminus:dev-pin-reflection-docblock" to perform the review.

[dearmond]

This branch fixed the CI issues for me. I did as @arosboro recommended. Worked great!

[rbayliss]

Just chiming in here to say that the temporary fix works for us as well. Thank you! Is there any possibility of getting a PHAR version of terminus primarily for use in CI? Seems like that would solve this issue pretty easily.

[ronan]

+1