mac 0.7.2

Mail is faster across the board. Every output is byte-identical to 0.7.1.

Command	0.7.1	0.7.2
mac mail list	257 ms	19 ms
mac mail unread	66 ms	18 ms
mac mail read <id>	41 ms	19 ms
mac mail mailboxes	44 ms	18 ms
mac mail mark-read <id> (dry run)	208 ms	17 ms
mac mail search from:github.com	40 ms	20 ms

• Listing ranks only the newest matches. Mail stores some messages more than once. list, unread and search used to rank every matching message to collapse those copies, then kept 20. Now they read the newest matches first and rank only those, whenever that can't change the answer.
• Finding a message by id uses Mail's own index. read, extract, reply, forward and every write used to scan all of Mail's message headers to find one id.
• mailboxes reads the unread counts Mail already keeps.
• Commands that change mail use the account cache too, so they no longer ask Mail.app for its account list on every run. Each write still targets an account by its id from Mail's index. --no-cache now works on every mail command that reads the account list.