Fix a bunch of links

.github/CONTRIBUTING.rst

@@ -155,7 +155,7 @@ However, you’ll probably want a more traditional environment as well.
 We highly recommend to develop using the latest Python 3 release because ``attrs`` tries to take advantage of modern features whenever possible.
 
 First create a `virtual environment <https://virtualenv.pypa.io/>`_.
-It’s out of scope for this document to list all the ways to manage virtual environments in Python, but if you don’t already have a pet way, take some time to look at tools like `pew <https://github.com/berdario/pew>`_, `virtualfish <http://virtualfish.readthedocs.io/>`_, and `virtualenvwrapper <http://virtualenvwrapper.readthedocs.io/>`_.
+It’s out of scope for this document to list all the ways to manage virtual environments in Python, but if you don’t already have a pet way, take some time to look at tools like `pew <https://github.com/berdario/pew>`_, `virtualfish <https://virtualfish.readthedocs.io/>`_, and `virtualenvwrapper <https://virtualenvwrapper.readthedocs.io/>`_.
 
 Next, get an up to date checkout of the ``attrs`` repository:
 

README.rst

@@ -95,7 +95,7 @@ Testimonials
   Writing a fully-functional class using attrs takes me less time than writing this testimonial.
 
 
-**Glyph Lefkowitz**, creator of `Twisted <https://twistedmatrix.com/>`_, `Automat <https://pypi.python.org/pypi/Automat>`_, and other open source software, in `The One Python Library Everyone Needs <https://glyph.twistedmatrix.com/2016/08/attrs.html>`_:
+**Glyph Lefkowitz**, creator of `Twisted <https://twistedmatrix.com/>`_, `Automat <https://pypi.org/project/Automat/>`_, and other open source software, in `The One Python Library Everyone Needs <https://glyph.twistedmatrix.com/2016/08/attrs.html>`_:
 
   I’m looking forward to is being able to program in Python-with-attrs everywhere.
   It exerts a subtle, but positive, design influence in all the codebases I’ve see it used in.

docs/examples.rst

@@ -329,7 +329,7 @@ And sometimes you even want mutable objects as default values (ever used acciden
    >>> cp
    ConnectionPool(db_string='postgres://localhost', pool=deque([Connection(socket=42)]), debug=False)
 
-More information on why class methods for constructing objects are awesome can be found in this insightful `blog post <http://as.ynchrono.us/2014/12/asynchronous-object-initialization.html>`_.
+More information on why class methods for constructing objects are awesome can be found in this insightful `blog post <https://as.ynchrono.us/2014/12/asynchronous-object-initialization.html>`_.
 
 Default factories can also be set using a decorator.
 The method receives the partially initialized instance which enables you to base a default value on other attributes:

docs/why.rst

@@ -138,7 +138,7 @@ With ``attrs`` your users won't notice a difference because it creates regular,
 …Data Classes?
 --------------
 
-:pep:`557` added Data Classes to `Python 3.7 <https://docs.python.org/3.7/whatsnew/3.7.html#pep-557-data-classes>`_ that resemble ``attrs`` in many ways.
+:pep:`557` added Data Classes to `Python 3.7 <https://docs.python.org/3.7/whatsnew/3.7.html#dataclasses>`_ that resemble ``attrs`` in many ways.
 
 They are the result of the Python community's `wish <https://mail.python.org/pipermail/python-ideas/2017-May/045618.html>`_ to have an easier way to write classes in the standard library that doesn't carry the problems of ``namedtuple``\ s.
 To that end, ``attrs`` and its developers were involved in the PEP process and while we may disagree with some minor decisions that have been made, it's a fine library and if it stops you from abusing ``namedtuple``\ s, they are a huge win.