Disable PHP output buffering when reading file contents (fixes #389)

[smaarn]

Basically I was facing the same issue as in #389 and there was always the option of playing with the PHP options but I wonder if the buffering shouldn't be disabled altogether in this kind of process.

So here the idea was to simply flush the output buffer and stop using it and then read the file contents.

Two notes:

1. In terms of performance I'm not a guru enough to be able to assess whether buffering adds a lot of value here. But there may be cases where it has so this could be the wrong path
2. When opening the file in read mode a "read lock" was put on the file before reading the file size. By reading the file contents brutally without opening the file handle there is a risk for having inconsistent data (if file is changed basically between the reading of the file size and the reading of its contents). But that seemed farfetched to me.

But I also may be missing something here :)

[mikespub]

Replaced by equivalent #518
Included in #522 and release 1.2.2 at https://github.com/mikespub-org/seblucas-cops

[smaarn]

Replaced by equivalent #518
Included in #522 and release 1.2.2 at https://github.com/mikespub-org/seblucas-cops

@mikespub thanks for the heads-up ! I will therefore be closing this MR and switch to the forked version.