Merge pull request #55 from ekweirui/update-user-guide

Update user guide to directly address user (contacts)

docs/UserGuide.md

@@ -210,10 +210,11 @@ This command will require two flags, and one optional flag:
 * `e/`: To be followed by the email of the new contact.
 * `p/`: (Optional flag) To be followed by the phone number of the new contact.
 
-Format: `add contact n/NAME e/EMAIL p/PHONE_NUMBER`
-* Specifying a phone number is optional.
-* When adding a duplicate name, Plannit will display an error message.
-* Phone numbers are compulsory to be exactly 8 digits and without country code.
+Format: `add contact n/NAME e/EMAIL [p/PHONE_NUMBER]`
+* You cannot add a duplicate name into Plannit.
+* You may optionally specify a phone number.
+* You cannot specify any country code for phone number.
+* You cannot specify a non-8-digit phone number.
 
 Examples:  
 ```
@@ -233,7 +234,7 @@ This command will require one flag:
 * `n/`: To be followed by the to-be-deleted contact name.
 
 Format: `delete contact n/NAME`
-* If the provided `NAME` does not exist in Plannit, Plannit shows an error message.
+* You cannot delete a non-existent contact.
 
 Example:  
 ```