Improve performance, err handling & readability

1. Download your OS's version of the program from below.
   • TypeScript_to_JavaScript.exe: Windows
   • TypeScript_to_JavaScript: Linux
2. Add a scripts.ts file in the same directory, or remember to set the -file command-line-argument if it is outside the program's directory.
3. Run the program with the following potential flags:

-file string
    Path to the TypeScript file. (default "scripts.ts")
-minify bool
    Minify the JavaScript output.
-stream float64
    File streaming minimum threshold in megabytes. (default 2.5)