use tabs, not spaces

TODO.md

@@ -1,14 +1,14 @@
 ## TODO:
 1. Multiple functions in one graph.
-    - Backend support
-        - Integrals between functions (too hard to implement, maybe will shelve)
-    - UI
-        - Different colors (kinda)
+	- Backend support
+		- Integrals between functions (too hard to implement, maybe will shelve)
+	- UI
+		- Different colors (kinda)
 2. Rerwite of function parsing code
-    - Non `y=` functions.
+	- Non `y=` functions.
 3. Smart display of graph
-    - Display of intersections between functions
-    - Caching of roots and extrema
+	- Display of intersections between functions
+	- Caching of roots and extrema
 4. Fix integral line
 5. re-add euler's number (well it works if you use capital e like `E^x`)
 6. allow constants in min/max integral input (like pi or euler's number)