Some changes

[agentjill]

@MathNya, in theme of making changes as felt necessary, In this PR I have made the same.

• General chages
• In src/helper/coordinate.rs, the major change was for logical checking in function adjustment_insert_coordinate(..), additional check not necessary as guaranteed by compiler because of function signature being u8. More details mentioned at points individually.
• In src/structs/coordinate.rs a to_string() method was added to struct Coordinate because the name get_coordinate() didnt match to its function. The use of later was changed to wherever mentioned in the crate but not removed due to breaking change.
• In src/writer/driver.rs the inbuilt function extend_attributes(..) was used in place of the manual implementation.
• In src/helper/html.rs there are some changes in pub trait potentially leading to breaking change. I felt this necessary because functions returning bools weren't named so to reflect same.
• changed the match statements where only one path was followed to if let syntax for clarity purposes. Also, inverted several of the if statements for clarity purposes.

[MathNya]

@agentjill Thank you for the great correction. We have confirmed that there are no problems and will merge them in.