Updated README
Finished the type system.
Added a large amount of core functions.
Finished a primitive interpreter that takes a list of tokens and
executes it on an interpreter state.

Redid the Token type. Instead of having separate types for string,
number, etc. literals, they are now unified under the type LTok.
Added a stub parser. Finalised the Interpreter module.
Finished a basic version of the interpreter. Currently compiles and executes an expression given on the command line. Majority of standard functions still not supported.
Major update (breaking).

Changelog:
 - When stringified, lists are bounded by {} rather than ().
 - Added tests.
 - Added () syntax for string literals.
 - Added some functions.