Question: Dick Costolo was the CEO of which company before the co-founder took over in 2015?
Context: Jeff Annison is an American businessperson, and co-founder and president of Legion M, the world's first fan-owned entertainment company.  Annison is also the co-founder and CEO of New York Rock Exchange, co-founder and CEO of Underground Labs, and co-founder of MobiTV. Richard William "Dick" Costolo ( ) was the CEO of Twitter from 2010 to 2015; he also served as the COO before becoming CEO.  He took over as CEO from Evan Williams in October 2010.  On June 11, 2015, it was announced that Costolo would step down as CEO on July 1, 2015 and would be replaced by Twitter co-founder and chairman Jack Dorsey on an interim basis until the Board of Directors could find a replacement.  On August 8, 2015, The New York Times reported that Costolo would be leaving Twitter's Board of Directors by the end of the year or when a new CEO is appointed. Evgeny Pluzhnik (Russian: Евгений Владимирович Плужник ; March 6, 1975, Karazhal, Kazakhstan) - Vice-Rector of the Moscow Technological Institute (MosTech), CEO of Moscow Business School, co-founder of Numbuster LTD, co-founder and CEO Robototechnika Ltd, investor Promobot, investor AnyWalker, investor BiTronics Lab, co-founder NVR, senior partner at consulting company «Legal Bridge», Member of the Advisory Council of the Russian unit of annual global survey-ranking countries' competitiveness (IMD World Competitiveness YearBook). Keith Nellesen (born 1967) is an American entrepreneur and the co-founder of Vivint, Inc., a home automation, security and solar energy company.  Vivint, Inc. was acquired in late 2012 for $2.2 Billion by the Blackstone Group.  Following the sale of Vivint to the Blackstone Group, Nellesen became the founder of NUVI where he is currently the CEO.  Nellesen has been a part of NUVI since its founding and previously served as the CEO of the company from May 2014 to October 2015, before recently resuming the CEO position in late 2016.  He also previously served as Chairman and CEO at MoneyReef. Jonathan M. Ansell (born August 13, 1950 in Binghamton, New York) is an American entrepreneur and CEO in the insurance and insurtech industry.  Ansell is the founder and CEO of insurtech companies Merlinio Technologies and Merlinio Insurance Services, an online digital insurance agency and technology platform serving the millennial market.  Before Merlinio, Ansell was a co-founder and CEO of Fusion Company, a global digital merchandising provider that specializes in ancillary products.  Fusion was created in 2012 after being spun-out of a large international insurance company.  Previously Ansell was the President, CEO and one of the co-founders of what is now Allianz Global Assistance USA, one of the largest travel insurance companies in the US and American specialty insurer Jefferson Insurance Company.  He was also a member of the management board of Allianz Global Assistance, formerly Mondial Assistance, an international travel insurance and assistance company based in Paris, France. Brad Keywell (born October 1969) is an entrepreneur based in Chicago.  He is co-founder and CEO of Uptake, a predictive analytics SaaS platform provider that empowers companies in major industries to optimize performance, reduce asset failures and enhance safety.  He is a Managing Partner and co-founder of Lightbank, a venture fund investing in disruptive technology businesses.  He is a co-founder and director of Groupon.  He is a co-founder and director of Mediaocean, which provides integrated technology operating systems to the advertising and media buying industry.  He is a co-founder and director of Echo Global Logistics, a technology-based enterprise transportation management firm.  In 2015 Brad and his wife Kim took The Giving Pledge to give away half of their wealth.  He is an Adjunct Professor at the Booth School of Business at the University of Chicago, teaching a course along with Eric Lefkofsky entitled "Building Internet Startups." FeedBurner is a web feed management provider launched in 2004.  FeedBurner was founded by Dick Costolo, Eric Lunt, Steve Olechowski, and Matt Shobe.  Costolo is a University of Michigan graduate, and was CEO of Twitter from 2010 to 2015.  FeedBurner provides custom RSS feeds and management tools to bloggers, podcasters, and other web-based content publishers. Martin Shkreli ( , born March 17, 1983) is an American businessman, former hedge fund manager, and convicted felon.  He is the co-founder of the hedge funds Elea Capital, MSMB Capital Management, and MSMB Healthcare; co-founder and former chief executive officer (CEO) of the biotechnology firm Retrophin; and founder and former CEO of Turing Pharmaceuticals.  Shkreli is also the CEO of start-up software company Gödel Systems, which he founded in August 2016. Richard L. "Dick" Kinzel (born July 25, 1940) is the former CEO of Cedar Fair Entertainment Company.  He served as president and CEO of Cedar Fair until January 2, 2012, when his successor, Matt Ouimet, took over as president and CEO.  He was involved in Cedar Fair for 39 years. Jack Dorsey (born November 19, 1976) is an American computer programmer and internet entrepreneur widely known as a co-founder and CEO of Twitter, and as the founder and CEO of Square, a mobile payments company.  In 2008, he was named to the "MIT Technology Review" TR35 as one of the top 35 innovators in the world under the age of 35.  For 2012, "The Wall Street Journal" gave him the "Innovator of the Year Award" for technology.
Answer: Twitter