Prepare for crates.io publication

- Fix unused variable warnings in tests
- Remove unused imports
- Ready for v0.3.0 release

Author: Nonanti

examples/scientific_computing.rs

@@ -1,8 +1,5 @@
 use mathcore::parser::Parser;
-use mathcore::{
-    differential::{DifferentialEquations, PDESolver},
-    MathCore,
-};
+use mathcore::differential::{DifferentialEquations, PDESolver};
 
 fn main() {
     println!("Scientific Computing Examples\n");

tests/integration_test.rs

@@ -6,7 +6,7 @@ fn test_complete_workflow() {
     let math = MathCore::new();
 
     // Parse expression
-    let expr = MathCore::parse("x^2 + 2*x + 1").unwrap();
+    let _expr = MathCore::parse("x^2 + 2*x + 1").unwrap();
 
     // Evaluate with variables
     let mut vars = HashMap::new();
@@ -15,10 +15,10 @@ fn test_complete_workflow() {
     assert_eq!(result, 16.0);
 
     // Differentiate
-    let derivative = MathCore::differentiate("x^2 + 2*x + 1", "x").unwrap();
+    let _derivative = MathCore::differentiate("x^2 + 2*x + 1", "x").unwrap();
 
     // Integrate
-    let integral = MathCore::integrate("2*x + 2", "x").unwrap();
+    let _integral = MathCore::integrate("2*x + 2", "x").unwrap();
 
     // Solve equation
     let roots = MathCore::solve("x^2 + 2*x + 1", "x").unwrap();