Added version number verification against github API using tag names

Well, it is a coding standard rule which has been set this way. The codebase was already using this style before I joined the community (nearly 4 years ago now) (even though we wrote the docs about the standard much later) so I was not there for the choice.

Then, it is a matter of consistency in the codebase. Both styles are OK, as long as your codebase is consistent.
However, given that the goal is to make this tool an official Symfony project (hence its namespace), it makes sense to follow the Symfony rules