Added better logging with different logging levels

Creates a (new) logfile stored in the root folder, named `ice.log`. This can easily be pointed to the old `log.txt` however.

By using the `logging` module, it is easy to decide which information you want store in the stream handler (terminal output) and file handler (logfile).

Example terminal output:
`[marcus@archlinux-desktop Ice]$ python2 ice.py 
2013-12-23 23:57:03,707 (ice) INFO: Starting Ice
2013-12-23 23:57:03,710 (ice) INFO: Skipping DS (no emulator provided)
2013-12-23 23:57:03,710 (ice) INFO: Skipping SNES (no emulator provided)
2013-12-23 23:57:03,711 (ice) INFO: Skipping PS2 (no emulator provided)
2013-12-23 23:57:03,711 (ice) INFO: Skipping PS1 (no emulator provided)
2013-12-23 23:57:03,711 (ice) INFO: Skipping NES (no emulator provided)
2013-12-23 23:57:03,711 (ice) INFO: Skipping Dreamcast (no emulator provided)
2013-12-23 23:57:03,711 (ice) INFO: Skipping GBA (no emulator provided)
2013-12-23 23:57:03,712 (ice) INFO: Skipping Genesis (no emulator provided)
2013-12-23 23:57:03,712 (ice) INFO: Skipping Gamecube (no emulator provided)
2013-12-23 23:57:03,712 (ice) INFO: Skipping N64 (no emulator provided)
2013-12-23 23:57:03,712 (ice) INFO: Skipping Wii (no emulator provided)
2013-12-23 23:57:03,712 (ice) INFO: Skipping Gameboy (no emulator provided)
2013-12-23 23:57:03,713 (ice) INFO: Running for user 20421584
2013-12-23 23:57:03,713 (ice) INFO: Downloading grid images
2013-12-23 23:57:03,714 (ice) INFO: Ice finished

Close the window, or hit enter to exit...`

Everything should be working without problem, as I've just replaced the new logging methods with the old ones.