Release GIL and multi file programs.

This release fixes various bugs from v0.1.1 and adds new features. Here's the changelog:

Bug fixes

• Fixed bug that prevented proper loading of files from CLI.

Features

• Added no_gil block support.
• Allow creating instance variables.
• Multiple file Rubex programs using rubex_require.
• Support multiple arguments in [] operator.
• New rake tasks for various options like debug, just compiling, compile + install etc.
• More CLI options for debug and force.

Refactoring of existing codebase

This is a patch update that includes a major revamp of almost the entire codebase. The user-level behaviour is the same and there are no breaking changes.