Bump astroid from 2.0.4 to 2.4.2 (#75)

Bumps [astroid](https://github.com/PyCQA/astroid) from 2.0.4 to 2.4.2.
- [Release notes](https://github.com/PyCQA/astroid/releases)
- [Changelog](https://github.com/PyCQA/astroid/blob/master/ChangeLog)
- [Commits](pylint-dev/astroid@astroid-2.0.4...astroid-2.4.2)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_dev.txt

@@ -1,5 +1,5 @@
 -i https://pypi.python.org/simple
-astroid==2.0.4
+astroid==2.4.2
 bleach==3.2.2
 certifi==2018.10.15
 cffi==1.11.5