Added chi2 to fit results (#131)

- fit_gaus and fit_pol1 now return a dict
- calculate chi2 after fit
- cleaned up code

CMakeLists.txt

@@ -85,7 +85,7 @@ if(AARE_FETCH_LMFIT)
         GIT_TAG        main
         PATCH_COMMAND ${lmfit_patch}
         UPDATE_DISCONNECTED 1
-        EXCLUDE_FROM_ALL
+        EXCLUDE_FROM_ALL 1
     )
     #Disable what we don't need from lmfit
     set(BUILD_TESTING OFF CACHE BOOL "")