Allow shell quoting on CLI

Break up command-line args using shlex rather than string.split

This enables multiple-word tags using quotes:

mailpile> tag/add "three word tag"
mailpile> tag +"three word tag" 20
type="text/javascript" is redundant

<script> elements only need an explicit type when it is something
other than JavaScript.
Simplified author list in README.md

Instead of filtering the complete git log, `git shortlog -s` (‘s’ for “summary”) can be used to view a list of authors with the number of their respective commits. `git shortlog` also has the benefit of respecting a .mailmap file if it exists, which allows to fix incorrect e-mails or names.
 In addition, Github also offers a list of contributors.
install_requires corresponding to pip requirements

So that `python setup.py install` yields a functional Mailpile.
Update README.md with missing community link

Update README.md with missing community link
[Issue #398] Fix the help/variables command and API endpoint
[Issue #398] Add simple test and better displaying for help/variables
Ignore expired or revoked secret keys during setup
Removed uneeded type=text/javscript as per Issue #391
Enable jinja2 autoescaping
Fixes to command result messages, mark more strings for translation
Allow jinja2 templates for txt, js, css, xml and rss formatted results
Add GPG fingerprints to addresses on reply (Issue #386)
Fixing merge conflict from Pull request
Merge pull request #407 from Cathryne/master

Update README.md with missing community link
Merge pull request #401 from lucaswerkmeister/patch-1

Simplified author list in README.md
Fixed a missing NoSuchMailboxError import statement
Fixed another missing import statement.
python-jinja2 listed as dependency for Debian
spambayes package suggested to Debian users