Improve import mechanism
Currently when I use the recommended mechanism of doing `require('monero-javascript')` my sensible editor wonders where I'm pulling the suddenly defined classes from. While the code itself works this is quite annoying as it would require me to disable eslint. Furthermore importing everything always is not very efficient. I see that when you import monero-javascript what is actually being done in the background is that a function is called that globally defines all the classes and functions. Could you please use a standard form of module exports? I'd much appreciate it!