Filling out a little bit of the lexer interface to gauge progress.

* Static factory that takes a file and creates a Lexer
* Lexer's constructor now takes universal reference (cause why not)
* Lexer's contents have newlines stripped out
* Lexer's interface method is now camelCase
Can you change this to just be `AsString` or `ToString`? That way when we start saving the string piece we can include it in the string output.