Update spec theme to show incubation status

Since ironic is an incubation project, it should be using the
incubation option in oslosphinx.

Change-Id: I28899f5d8af36846948b468b94fef8622e4bc30d

doc/source/conf.py

@@ -97,7 +97,7 @@ html_theme = 'nature'
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the
 # documentation.
-#html_theme_options = {}
+html_theme_options = {'incubating': True}
 
 # Add any paths that contain custom themes here, relative to this directory.
 #html_theme_path = []

requirements.txt

@@ -1,5 +1,5 @@
 docutils==0.9.1
-oslosphinx
+oslosphinx>=2.2.0.0a2
 pbr>=0.6,!=0.7,<1.0
 sphinx>=1.1.2,<1.2
 testrepository>=0.0.18