IFSFIT: Integral Field Spectroscopy FITting

First release. IFSFIT is a general-purpose library for fitting the continuum, emission lines, and absorption lines in integral field spectra (IFS). It uses PPXF (the Penalized Pixel-Fitting method developed by Cappellari & Emsellem, 2004, PASP, 116, 138) to find the best fit stellar continuum (using a user-defined library of stellar templates and including additive polynomials), or optionally a user-defined method to find the best fit continuum. It uses MPFIT to simultaneously fit Gaussians to any number of emission lines and emission line velocity components. It will also fit the NaI D feature using analytic absorption and/or emission-line profiles, or a generic absorption-line doublet or multiplet function (such as MgII 2796/3802).