Updated TODO

TODO.md

@@ -1,11 +1,11 @@
  - Minimize parenthesis when printing expressions
  - Consistent errors:
    - Consistent look
-   - Linelocation for math errors
    - Undefined error?
    - Better error when `sin = 2`
    - Check syntax when parsing or when evaluating?
  - list and delete variables
+ - sin() with units (rad and deg)
 
 ## Pre-release
  - Commands to list constants, units, and substitutions