You made a commitment to the company by agreeing to a vesting schedule — the company should reciprocate and commit to you by granting acceleration upon termination.
Babak Nivi is a co-founder of AngelList and Venture Hacks. Previously, he was an entrepreneur-in-residence at Bessemer Venture Partners and Atlas Venture. He has worked on startups including Songbird, Grockit, and Kovio. He went to school at MIT where received 2 patents and published in Science.