[New Plugins] spellcheck, uniquotes, redirects

[andreacorbellini]

I would like to contribute the following 3 plugins, that I'm currently using on my blog:

• spellcheck: https://github.com/andreacorbellini/andreacorbellini.github.io/blob/master/src/plugins/spellcheck.py
  Runs a spell checker on your articles and pages at generation time. Currently based on aspell.
• uniquotes: https://github.com/andreacorbellini/andreacorbellini.github.io/blob/master/src/plugins/uniquotes.py
  Replaces ascii quotes " and ' with their unicode equivalent depending on the context, for example: "it's a 'sunny' day" becomes “it’s a ‘sunny’ day”.
• redirects: https://github.com/andreacorbellini/andreacorbellini.github.io/blob/master/src/plugins/redirects.py
  Lets you specify an alias in your articles and pages. If set, an html file with the name of the alias is created with the purpose of redirecting to the original article/page (example usage and output).

Before submitting these plugins to the pelican-plugins organization I plan to add tests and add a little more configuration options. These will be released under a permissive license—usually I like the BSD-3-Clause license.

Thanks for your consideration!