First stage install documentation improvements.
Start re ordering the advanced docs.
Much improved installation documentation.

Uses some of the testing changes in sunpy/sunpy#1180.
Build with the RTD theme if it is installed.
Small tidy up to the install step.
Improvements to the install commands.

pip install with no deps so you don't get source version overrides and
use suds-jurko.
More updates to reflect comments.
more advanced install improvements.
change troubleshooting section to standard install instructions.
comment mock / scikit-image in conf.py
Small changes to platform specific instructions.

Remove anaconda from platform specific and generally tweak a little.
more sphinx link fixes.
Remove windows alternative docs and correct typos.
Merge pull request #1181 from Cadair/install_doc_update

[Review]: Large installation documentation update.