Show tail of large log file
Currently, if the log file is large, CircleCI shows the log starting from the beginning. This is usually not useful since if something failed it is generally at the end of the log file. Instead, CircleCI should show the end (tail) of the log file (and still give the prompt to download the entire log).
Similarly, when a build that has a lot of output is running, CircleCI should continue to display only the tail of the file so that you can tell if the build is continuing to run and where in the build process it is currently at.