Reject Error Values in Arguments

0.3.2 (2019-11-05)

• Incompatible Change: Error values are no longer allowed as function arguments.
  This greatly improves the situation where error values linger around in
  data structures or get written out unintentionally. With this the risk of
  unintentionally ignoring an error is mitigated.
• Feature: Calling numbers with strings and byte vectors returns the
  character or byte substring at that index (based on 0). This is symmetrical,
  you can also call a string or a byte vector with an integer to get the
  same result.
• Feature: Added std:io:file:read_text, std:io:file:read, std:io:file:write_safe
  and std:io:file:append.
• Bugfix: VValUserData get_key() was never called.
• Feature: Added VValUserData::call() to make VValUserData callable.
• Bugfix: LocalFileModuleResolver now properly inherits the loaded modules from the
  parent GlobalEnv.
• Feature: Added SymbolTable::set() for setting variables that are provided by a module
  from Rust.
• Feature: Added many std:num:* functions (still undocumented)
• Feature: Added std:hash:fnv1a, and std:rand:split_mix64_* functions.