Restructuring

[ebcrowder]

• adds more robust logic for better error handling and messaging
• moves the logic contained in the various modules into struct methods. This improves readability but also removes duplicate and unnecessary data structures.
• rename the modules to singular verbs for consistency
• replace integration tests with unit tests. Right now, the tests don't add a ton of value as they do not assert the stdout output but this is a good starting place. Besides, the previous tests did not add a lot of value, either.
• compile times are much faster because we were able to drop hefty dev dependencies that were used by the integration tests.
• dependency updates

[ebcrowder]

alrighty @dantuck - this is ready to go now.

Since it has been a while since I have published a version of this to crates.io, I'll do that after this gets merged.

[dantuck]

This looks really good. Nice work! I made a suggestion on the error result if you would like to take it. Other than that this looks like a good restructure.

As a follow up maybe we can chat about cleaning up the error output a little so that it doesn't look so programmer like:

➜  rust_ledger git:(fs) RLEDGER_FILE=examples/example.yal cargo run register 
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running `target/debug/rust_ledger register`
Error: IOError(Os { code: 2, kind: NotFound, message: "No such file or directory" })

would become:

➜  rust_ledger git:(fs) RLEDGER_FILE=examples/example.yal cargo run register 
    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running `target/debug/rust_ledger register`
No such file or directory

Or something similar. I have been making some implementation changes to error output in another project that you could probably implement here.

[dantuck]

I like this change going to singular. Clean and consistent with the other commands.

[dantuck]

You could add:

/// A type alias for `Result<T, Error>`.
pub type Result<T> = result::Result<T, Error>;

Which would allow you to change:

pub fn register(filename: &String, option: &String) -> Result<(), Error>

to

pub fn register(filename: &String, option: &String) -> Result 

[ebcrowder]

This a nice shortcut - thanks!

[dantuck]

And now that is CLEAN!

[ebcrowder]

Or something similar. I have been making some implementation changes to error output in another project that you could probably implement here.

Great - please do let me know what you find. I spent some time trying to figure out how to parse the default Error output but couldn't figure out a way to do it. I'm guessing the display() fn would be the place to do it.

I'll merge this in the meantime. Appreciate the quick review!