cli: swap order of inbox and outbox in status

I want to see the inbox more often than the outbox, and a long outbox causes me
to have to scroll up to see the inbox if the inbox is displayed first.
Avoid SafeTempDir with odd permissions.

We actually need rwx permissions, so check for it.
Reverse order of cli global/context help output

Fixes #70
Don't panic on gtkspell errors

gtkspell.New() returns an error if it fails to find a dictionary for the
current locale. Instead of panicing, just print the error to stderr and
continue without the spell checker.

"Fixes" issue #68
Merge branch 'ebfe-tmpdir-perms'
No need to call error.Error() when formatting as a string.
Merge branch 'ebfe-gtkspell-panic'
Merge branch 'ebfe-issue-70'
Add save-key command and fix crash.

Previously if one attempted to download a detachment that wasn't
uploaded then the CLI would crash. This change fixes that and also adds
the save-key command to just save a key to disk. The decrypt utility, in
this repository, can be used to decrypt with the key.
Go 1.0 compat fix.

Fixes #56.