added shrink_to_fit function
fixed a few potential bugs, a new bug with adding a double appeared
Merge https://github.com/raeanne-marks/C-Vector
fixed the same potential bugs, still weird addDouble error
Merge https://github.com/raeanne-marks/C-Vector
fixed the realloc bug, made some changes to prevent bugs
Merge https://github.com/raeanne-marks/C-Vector