Rename vector to Vector

vector.h

 #define VECTOR_H
 
 /**
- * A structure to represent 2d vectors
+ * A structure to represent 2D vectors.
+ * Note that this line declares a "struct vector" type
+ * and aliases it to "Vector".
  */
-typedef struct vector vector;
+typedef struct vector Vector;
 
 /** @brief Allocates memory for and initializes a vector
  *         to have x-component x and y-component y
  *  @param y the character to print
  *  @return a new vector that represents <x, y>
  */
-vector *vec_init(double x, double y);
+Vector *vec_init(double x, double y);
 
 /** @brief Frees the memory associated with vec
  *
  *  @param vec the vector to free
  *  @return Void.
  */
-void vec_free(vector *vec);
+void vec_free(Vector *vec);
 
 /** @brief Returns a new vector that represents the sum of v1 and v2
  *
  *  @param v2 a vector
  *  @return a vector that represents the sum of v1 and v2
  */
-vector *vec_add(vector *v1, vector *v2);
+Vector *vec_add(Vector *v1, Vector *v2);
 
 #endif
\ No newline at end of file