* Prepare 7.9.0 release

* Put back the v7.8.0 version

We need this to ensure the versioning used during testing on GitHub.com doesn't cause caching problems in future

* fix errors on non-UTF-8 encodings

Some files failed with "invalid byte sequence in UTF-8 (ArgumentError)"
when BlobHelper#lines was called. Some problematic files include
UTF-16LE samples such as test/fixtures/Data/utf16le.

Errors were not present when computing stats from git repositories,
since git blobs are always read as ASCII-8BIT and that was working
correctly. However, when using FileBlob, encoding could be ASCII-8BIT,
UTF-8 or other, depending on the runtime value of Encoding.external_encoding.

Tests were not catching the error since they were forcing
Encoding.external_encoding to be ASCII-8BIT (introduced in #1211). So the
error would only be seen in wild usage (see issue #353).

This commit forces ASCII-8BIT on File.read calls. The error is still
present if using memory blobs with other encodings.

* Decrease expected error count

* Set version to 7.9.0

Co-authored-by: Rick Winfrey <[email protected]>
Co-authored-by: Santiago M. Mola <[email protected]>