Add wcscheck utility

Add documentation for wcslint
Fix for Python 2.6, which is missing PyErr_NewExceptionWithDoc
Fix Python 3 issues
Some superfluous whitespace fixes
Adds a test and kind of hacky fix for #1244. Basically we try to decode the byte string using locale.getpreferredencoding(), but if that returns an invalid encoding we try decoding with utf-8. If that fails (do to undecodable bytes) we just fall back on latin-1.  Therefore we always output *something* though there's no 100% guarantee it won't be gibberish if the system's default encoding is incorrect.
Document the new `tests.helper.catch_warnings` context manager.
Use `tests.helpers.catch_warnings` instead of `warnings.catch_warnings`
Merge pull request #1244 from iguananaut/issue-1244

Problems with logging in some systems
Merge pull request #1265 from mdboom/testing/use-catch-warnings

Use astropy.tests.helpers.catch_warnings instead of warnings.catch_warnings
PEP8 spacing fix
Allow non-strings to be logged without raising a TypeError
Merge pull request #1267 from barentsen/allow-logging-non-strings

Allow non-strings to be logged without raising a TypeError
Merge pull request #580 from mdboom/wcs/lint

Consider having a wcscheck utility
Add the release date of 0.2.3 and add a placeholder for 0.2.4.