add support to rtd_theme without is installation

Signed-off-by: sebgoa <sebgoa@sebimac.local>
replace hardcoded version by |version| or |release| variables

Signed-off-by: sebgoa <sebgoa@sebimac.local>
rnotes.rst: replace ubuntu repos to 4.3: This closes #7

Signed-off-by: sebgoa <sebgoa@sebimac.local>
change URL of guides