Fix Sphinx warnings found when building.

includes_config/includes_config_rb_11-4_client_settings.rst:101: WARNING: Inline substitution_reference start-string without end-string.
includes_environment_variables/includes_environment_variables_child_processes.rst:52: ERROR: Undefined substitution referenced: "resource bash".
includes_environment_variables/includes_environment_variables_child_processes.rst:70: ERROR: Undefined substitution referenced: "resource bash".
Merge pull request #125 from juliandunn/fix-sphinx-warnings

Fix Sphinx warnings found when building.