Added example that triggers exceptions
Throw IrresolvableSymbolException in SymbolResolver
Added custom RuntimeException that overrides stack trace
Added some convenience methods to DefinitionTable
Show custom backtrace with Interpres filename and line number
Throw custom FileNotFoundException for invalid require statements
Added exception handling demo
Rethrow antlr exceptions as runtime exceptions, not sure if best approach
Cleaned up Require#invoke
Added fix for halting executing when parsing fails