Fixed forgotten test.

Prettier REPL header and stuff.

Fixed string_shuffle function for unicode characters.

Repl mode - fixed occasional bug in handling multiline input.

Expanded tests to cover new cases.

Removed some of PHP versions from tests.

Optimized is-numeric-detection in NumberValue class a bit.

Updated language reference to include control structures.

Merge pull request #15 from smuuf/logicexpr

Logic expressions and other stuff

Merge pull request #14 from smuuf/strict

Handling of strings and numbers is now strict