[ENHANCEMENT] fs - proper error handling

[DetachHead]

Is your feature request related to a problem? Please describe.
currently I/O errors are caught in a try/catch and simply return true or false depending on whether or not it was successful.

this makes it difficult to debug as the return value false provides no information as to what went wrong

Describe the solution you'd like
these methods in FileSystem should just throw when they fail

Describe alternatives you've considered
perhaps a flag to change the error handling behavior, if you want the user to have the choice

Additional context
this made debugging difficult when implementing #83. i had to change the tryIfExists private method to throw instead when it fails, then changed it back such that it matches the behavior of the other targets.

[suparngp]

I agree, this totally makes sense. I vaguely remember why I did it this way in the first place. I think it was somewhat complicated to create a neat API which throws errors on ios and thats probably why, I chose to suppress the errors and return a flag instead. But it has been an year, so I can't say for sure.