Fix a few minor issues from clippy

src/differentiation/container_record/mod.rs

@@ -327,6 +327,7 @@ where
      *
      * This is a shorthand for `AsRecords::from(tensor.history(), TensorIterator::from(&tensor))`
      */
+    #[allow(clippy::type_complexity)]
     pub fn iter_as_records<'b>(
         &'b self,
     ) -> AsRecords<'a, TensorIterator<'b, (T, Index), RecordTensor<'a, T, S, D>, D>, T> {
@@ -529,6 +530,7 @@ where
      *
      * This is a shorthand for `AsRecords::from(matrix.history(), RowMajorIterator::from(&matrix))`
      */
+    #[allow(clippy::type_complexity)]
     pub fn iter_row_major_as_records<'b>(
         &'b self,
     ) -> AsRecords<'a, RowMajorIterator<'b, (T, Index), RecordMatrix<'a, T, S>>, T> {
@@ -543,6 +545,7 @@ where
      * This is a shorthand for
      * `AsRecords::from(matrix.history(), ColumnMajorIterator::from(&matrix))`
      */
+    #[allow(clippy::type_complexity)]
     pub fn iter_column_major_as_records<'b>(
         &'b self,
     ) -> AsRecords<'a, ColumnMajorIterator<'b, (T, Index), RecordMatrix<'a, T, S>>, T> {

src/matrices/mod.rs

@@ -781,7 +781,7 @@ impl<T> Matrix<T> {
             .into_iter()
             .map(|slices| {
                 let rows = slices.len();
-                let columns = slices.get(0).map(|columns| columns.len()).unwrap_or(0);
+                let columns = slices.first().map(|columns| columns.len()).unwrap_or(0);
                 if columns == 0 {
                     // We may have allocated N rows but if each column in that row has no size
                     // our actual size is 0x0

src/tensors/mod.rs

@@ -432,7 +432,7 @@ where
      * Returns a copy of the sole element in the 0 dimensional tensor.
      */
     pub fn scalar(&self) -> T {
-        self.data.get(0).unwrap().clone()
+        self.data.first().expect("Tensors always have at least 1 element").clone()
     }
 }
 
@@ -1127,7 +1127,7 @@ where
      */
     pub fn first(&self) -> T {
         self.data
-            .get(0)
+            .first()
             .expect("Tensors always have at least 1 element")
             .clone()
     }