UPDATE: Adds 'user model' API (#27)

* bump version for documentation
* Fixes wrong doc comment
* renames old APIs to be consistent

xlsx/examples/hello_calc.rs

@@ -1,5 +1,5 @@
 use ironcalc::{
-    base::{expressions::utils::number_to_column, model::Model},
+    base::{expressions::utils::number_to_column, Model},
     export::save_to_xlsx,
 };