Add tox.ini to the list of default config files

Because tox.ini is the latest addition to configuration files, it should
have the lowest priority. List it last in the documentation, but use the
reverse order in arguments of configparser.ConfigParser.read(), as I
suspect this functions overwrites options from prior configuration files
with options from subsequent configuration files.

Author: DimitriPapadopoulos

README.rst

@@ -94,9 +94,10 @@ Using a config file
 Command line options can also be specified in a config file.
 
 When running ``codespell``, it will check in the current directory for a file
-named ``setup.cfg`` or ``.codespellrc`` (or a file specified via ``--config``),
-containing an entry named ``[codespell]``. Each command line argument can
-be specified in this file (without the preceding dashes), for example::
+named ``.codespellrc``, ``setup.cfg`` or ``tox.ini`` (or a file specified via
+``--config``), containing an entry named ``[codespell]``. Each command line
+argument can be specified in this file (without the preceding dashes), for
+example::
 
     [codespell]
     skip = *.po,*.ts,./src/3rdParty,./src/Test

codespell_lib/_codespell.py

@@ -400,7 +400,7 @@ def parse_options(args):
     options = parser.parse_args(list(args))
 
     # Load config files and look for ``codespell`` options.
-    cfg_files = ['setup.cfg', '.codespellrc']
+    cfg_files = ['tox.ini', 'setup.cfg', '.codespellrc']
     if options.config:
         cfg_files.append(options.config)
     config = configparser.ConfigParser()