* mu4e: minor documentation update

Updating documentation to mention the second default keybinding for
'mu4e-headers-mark-for-something, '*', which was introduced in commit
c581468ac33fc753f06ce10a66a1ffaacc078df1.
* small doc fix
mu4e.texi: fix typo
Merge branch 'master' of github.com:djcb/mu
mu4e.texi: add hint about getting fields from raw messages

from a mailing-list reply, a quick & dirty way to get arbitrary headers
from a message.
Merge pull request #464 from anadrome/master

mu4e.texi: minor documentation update
Merge branch 'master' of github.com:djcb/mu
mu4e: make including dates in drafts optional (and disabled by default)

Add new configuration variable `mu4e-compose-auto-include-date'.