Daemail

-------------------
- Drop support for Python 3.5
- Support Python 3.9
- **Breaking**: All of the sending options have been removed from the
command-line interface. Sending is now performed via the
[`outgoing`](https://github.com/jwodder/outgoing) library, which is
configured via a configuration file.
- Errors that occur when daemonization is disabled will now be reported
directly to the screen instead of to the logfile

-------------------
- Massive internal rewrites
- Dropped support for Python versions earlier than 3.5
- Support Python 3.6 through 3.8
- Added a `--foreground` option for disabling daemonization
- **Breaking**: Removed `--to-name` and `--from-name` (deprecated in v0.5.0)
- **Breaking**: `--dead-letter`, `--logfile`, and `--mbox` now resolve symbolic
links before daemonization
- If no `--chdir` argument is supplied, change directory to the value of
`$PWD`, falling back to the old value of `getcwd()` only if the environment
variable isn't set
- `--encoding`, `--stderr-encoding`, and `--mime-type` arguments are now
validated before daemonization
- Deduction of the MIME type from `--stdout-filename`'s extension now better
handles names of compressed files

-------------------
- If an error occurs during daemonization (e.g., because the `--chdir` argument
is not a directory), a normal error traceback will be printed to stderr
instead of writing a report to the logfile.
- `--to-addr` can now be specified on the command line multiple times in order
to send to multiple addresses
- Arguments to `--to-addr` and `--from-addr` can now be in the form "`Real Name
<addressexample.com>`". `--to-name` and `--from-name` are now deprecated
and will be removed in a future version.

-------------------
- **Breaking**: `--dead-letter` and `--logfile` (and `--mbox`) are now resolved
relative to the directory in which daemail was started, not the directory
specified with `--chdir`
- **Breaking**: No more than one line ending sequence will be removed from
`--smtp-password-file` (for the unlikely case in which the password ends with
a newline)
- **Breaking**: Renamed `-m`/`--mail-cmd` to `-s`/`--sendmail`
- **Breaking**: Renamed `--err-encoding` to `--stderr-encoding` (The `-E` short
option remains unchanged)
- Local timestamps now include the timezone offset
- Added an `--mbox` option for "sending" e-mails to a local mbox file
- Gave `--chdir` a `-C` short form
- Gave `--split` an `-S` short form
- Added the `-i` option to the default `sendmail` command
- Added `--from-name` and `--to-name` options for setting the "real name" of
the sender & recipient
- Added a `--stdout-filename` option for specifying the name (and default MIME
type) of the stdout attachment
- Added `--netrc` and `--netrc-file` options for reading the SMTP username &
password from a netrc file
- Improvements to error message formatting

-------------------
First usable release