Update Windows Installation Instructions

[mickkilangston]

• Need to correct in Step 5 for windows: replace: %HOME%/hc with %HOME%\hc

also, to address issues with installing zmq; here's what I did that worked:

• download and unzip lib files from https://github.com/holochain/holochain-rust/tree/develop/vendor/zmq
• edit environment variables in system properties to add: LIBZMQ_PREFIX to point to that directory of zmq lib files (I created this both as a user variable and a system variable; not sure that both are required)

Doing this created a error when running "hc --version" in cmd that said, "libzmq-v140-mt-4_2_0.dll not found" This file is found in the above reference directory in the "bin" folder.

So, I moved libzmq-v140-mt-4_2_0.dll to the same folder where hc.exe lives --> and huzzah! It now works.

Things I don't know:

• are the other zmq files still required? meaning, is it just libzmq-v140-mt-4_2_0.dll that's needed?
• I did follow the process for building the zmq libraries using visual studio 2017 (per the instructions sort of given on http://zeromq.org/intro:get-the-software#toc10 ) -- however, while this did build successfully in VS17, my cmd was still throwing the error mentioned above. I haven't tested doing this installation from scratch with just the above method.

[Connoropolous]

https://developer.holochain.org/start.html