Add 3.0 info to README

[jgulledge19]

This is a start and would be helpful to add a bit more:

How to set up to contribute

From command line

• Fork the repo
• Use git clone to your PC or testing server
• Install Composer if not installed
• CD to the directory that you cloned into
• Run composer install

How to run Tests

A single test, via command line:

• cd test
• phpuint --bootstrap bootstrap.php "xPDO/Test/TearDownTest.php"

All tests

• cd test
• phpuint -c complete.phpunit.xml

v3.0 changes

• Use fully qualified names (FQN) for classes, schema and packages. And when passing classes to xPDO use double slashes.
  Example: xPDO\\Test\\Sample
• Schema files also must have FQN, see test/model/schema/xPDO.Test.Sample.mysql.schema.xml
• Do not use the addPackage() method as in v2, instead add your files to the composer to be auto included
  See Autoloading Composer
• New CLI tools
  • cd bin
  • Then php xpdo or php xpdo.php
  • Write XML schema, when you already have existing database tables (Not done)
    Example: php xpdo write-schema -C ../test/properties.inc.php mysql ../examples/test.schema.xml
  • Parse XML schema file, this will generate the PHP xPDO model classes
    Example: php xpdo parse-schema -C ../test/properties.inc.php -c --psr4 mysql ../examples/test.schema.xml ../examples/test/
    You will need the trailing slash