Add lifetime-fit
lifetime-fit: Add IRF offset
lifetime-fit: Fix covariance
Merge branch 'master' of goldnerlab:photon-tools
lifetime-fit: Fix output
lifetime-fit: Simplify
lifetime-fit: Fix join usage
lifetime-fit: Split only on lines
lifetime-fit: Fix up various things

 * Allow for shifted IRFs
 * Fit IRF background
 * Fix leastsq usage (off by square)