(Reuters) - Shares of online scrapbook company Pinterest Inc surged 25 percent in their debut on Thursday, giving it a market capitalization of $15.8 billion (£12.2 billion) and signalling increased investor appetite for new tech listings.The offering of 75 million shares was priced at $19, above the expected range of $15 and $17, and raised $1.4 billion in net proceeds.The shares opened at $23.75 and touched a high of $24.89 at of 1548 GMT.The company breezed past the $12 billion valuation it..