If he HATED you, he wouldn't have had lunch with you.
What were the circumstances of your having lunch with him? (1) Did he ask you to go to lunch with him? (2) Did you see him at the lunch room or restaurant and say hello, and then you ended up having lunch together? (3) Or were you eating lunch already, he saw you, and asked if he could join you? (4) Did you ask HIM to lunch? Your answer to these questions will change the answers to you.
(1) He asked you to go to lunch with him because he enjoys your company. It doesn't mean he's ready to become exclusive with you in a long-term relationship. It means he enjoys your company and wanted to spend some "casual" time with you. Had he wanted a more formal time with a bit more meaning to it, he would have asked you to join him for dinner.
(2) It was an accidental meeting, more or less, and he was being polite. Don't read too much into his asking you to join him. After you said hello to him, it would have been rude of him to have ignored you. Once you joined him, it was standard courtesy on his part to offer to pay for lunch. Again, don't read too much into it.
(3) He asked you if he could join you because yes, he likes you. If he didn't like you that much, then he would have waved hello and would have sat elsewhere. Again, it doesn't mean he wants to get into a long-term relationship with you, but it's more promising than #2.
(4) If you invited HIM and he paid for lunch, that doesn't mean much at all. It means he feels that "the gentleman should pay" when eating with a lady. It's common courtesy, and some men take that to be a measure of their "manliness"--they would NEVER let the woman pay for them. And it would also take a lot for them to allow the check to be split, etc. Read absolutely NOTHING into this one. The fact that he said yes to your invitation means about the same as in #1, where he asked YOU to lunch.