Inconsistent intersphinx link generation in docstrings

[tsbinns]

In #280 I noticed instances where ticks around class names where simply italicising words rather than rendering it as code and generating intersphinx links, especially for standard Python things like None, str, tuple, True, etc..., e.g.:

Should explicit intersphinx roles be provided to fix this, or should double ticks simply be used to render the text as code (but with no link, i.e., None)?

[drammock]

xref to my answer elsewhere: #280 (comment)

[tsbinns]

Okay, I'll go through later and fix the inconsistencies.

[tsbinns]

Sorted in #283