Added documentation for some functions and methods.

[psg-19]

I've submitted a PR to address this issue: #109
Tried documenting some of functions and methods.

[oleonardolima]

Thank you for working on this one!

I'd suggest: i) fixing some typos regarding the proper use of Rust's docstrings (i.e.: missing whitespace on /// Start...), checking the rustdoc book for more info see; ii) covering the documentations of more missing items to make the PR more substantial.

[psg-19]

fixed typos and added documentation to more public functions, methods, structs and traits I could find.
Please let me know if anything more needs to be done.