The startup AllTrails is popular with the hiking set, giving trailgoers a way to track their path up and down a mountain. Now it’s taking on real outside money to try and build a real business. Investors are putting $75 million toward the company in its first serious fundraising round — but one that will hand control over to Spectrum Equity. It’s money that it will use to hire and grow overseas and into diffferent languages, plus cash to buy out existing shareholders. The company depends on very little advertising but mostly paid subscriptions, claiming hundreds of thousands of hardcore hikers who pay $30 a year to gain access to things like overlays of upcoming weather and ways to share a route with friends. The company says it has 9 million registered users (including ones who pay nothing).