Fix for SourceBuffer failing on StreamSource

When empty StreamSource was provided (e.g. empty PSR-17 response body), reading would fail with "Uninitialized string offset: 0" due to missing buffer size check.

Fix for numbers in scientific notation

Most parsers allow scientific notation to have one or more leading zeros after "e". This patch addresses it, so 1.23e04, 1.23e+04, 1.23e-04, and so on, is allowed.

Support for JSON sequences

JSON sequences now correctly parsed if they have separators (coma/newline).
Full items of sequences can be retrieved with null as selector in items method.

First public release

This is feature-complete and mostly tested, so 1.0.

initial release

use older phpunit.xml format for using phpunit7/8 with older versions…

… of php while testing