Add notes section to readme, minor changes

Author: StBogdan

README.md

@@ -3,25 +3,25 @@
 > Existing Python solutions can be found [officially here](https://github.com/careercup/CtCI-6th-Edition-Python/tree/e6bc732588601d0a98e5b1bc44d83644b910978d) and [user-created here](https://github.com/w-hat/ctci-solutions)
 
 ### Current progress
-| Nr. 	|         Chapter        	| Done 	| Total 		| Ommited 	|
-|:---:	|:----------------------:	|:----:	|:-----:	|:-------:	|
-|   1 	| [Array and String](chapter_1)       	|   9  	|   9   	|       	|         	|
-|   2 	| [Linked Lists](chapter_2)           	|   8  	|   8   	|         	|
-|   3 	| [Stacks and Queues](chapter_3)      	|   6  	|   6   	|    1    	|
-|   4 	| [Trees and Graphs](chapter_4)       	|  12  	|   12  	|         	|
-|   5 	| [Bit Manipulation](chapter_5)       	|   8  	|   8   	|         	|
-|   6 	| [Math and Logic Puzzles](chapter_6) 	|  10  	|   10  	|    4    	|
-|   7 	| [OO Design](chapter_7)              	|   0  	|   12  	|         	|
-|   8 	| [Recursion and DP](chapter_8)       	|  14  	|   14  	|         	|
-|   9 	| [System Design](chapter_9)          	|   0  	|   8   	|         	|
-|  10 	| [Sorting and Searching](chapter_10) 	|   9  	|   11  	|    1    	|
-|  11 	| [Testing](chapter_11)                	|   4  	|   6   	|    4    	|
-|  12 	| [C/C++](chapter_12)                  	|  11  	|   11  	|    11   	|
-|  13 	| [Java](chapter_13)                   	|   0  	|   8   	|         	|
-|  14 	| [Databases](chapter_14)              	|   0  	|   7   	|         	|
-|  15 	| [Threads and Locks](chapter_15)      	|   0  	|   7   	|         	|
-|  16 	| [Moderate](chapter_16)               	|  26  	|   26  	|    1    	|
-|  17 	| [Hard](chapter_17)                   	|  26  	|   26  	|         	|
+| Nr. 	|         Chapter        	| Done 	| Total 		| Ommited 	| Notes |
+|:---:	|:----------------------:	|:----:	|:-----:	|:-------:	| :-------:	 |
+|   1 	| [Array and String](chapter_1)       	|   9  	|   9   	|       	|         	| |
+|   2 	| [Linked Lists](chapter_2)           	|   8  	|   8   	|         	| |
+|   3 	| [Stacks and Queues](chapter_3)      	|   6  	|   6   	|    1    	| |
+|   4 	| [Trees and Graphs](chapter_4)       	|  12  	|   12  	|         	| |
+|   5 	| [Bit Manipulation](chapter_5)       	|   8  	|   8   	|         	| |
+|   6 	| [Math and Logic Puzzles](chapter_6) 	|  10  	|   10  	|    4    	| |
+|   7 	| [OO Design](chapter_7)              	|   0  	|   12  	|         	| |
+|   8 	| [Recursion and DP](chapter_8)       	|  14  	|   14  	|         	| |
+|   9 	| [System Design](chapter_9)          	|   0  	|   8   	|       	| See [the System Design Primer](https://github.com/donnemartin/system-design-primer) |
+|  10 	| [Sorting and Searching](chapter_10) 	|   9  	|   11  	|    1    	| |
+|  11 	| [Testing](chapter_11)                	|   4  	|   6   	|    4    	| |
+|  12 	| [C/C++](chapter_12)                  	|  11  	|   11  	|    11   	| |
+|  13 	| [Java](chapter_13)                   	|   0  	|   8   	|         	| |
+|  14 	| [Databases](chapter_14)              	|   0  	|   7   	|         	| |
+|  15 	| [Threads and Locks](chapter_15)      	|   0  	|   7   	|         	| |
+|  16 	| [Moderate](chapter_16)               	|  26  	|   26  	|    1    	| |
+|  17 	| [Hard](chapter_17)                   	|  26  	|   26  	|         	| |
 
 
 ### Running the solutions