Clanvas

* Eagerly request courses in background on login.
* Tab-complete `wopen` command.
* Tab-complete the `-c` (`--course`) option for course-optional commands.
* Output directory (`-o`) option available to the `pullf` command.
* Assignment group grades and overall class grades shown in the `lg` command.
* Grades now colored based on score in the `lg` command.
* Quiet (`-q`) option available to the `login` command.

Added basic commands for navigating most basic resources.

| Command | Meaning |
|-----------|-----------------------|
| lc | list classes |
| cc | change current class |
| la | list assignments |
| lg | list grades |
| pullf | pull files |
| wopen | open in web interface |
| whoami | show login info |
| quit | quit the shell |