Maybe adjust install instructions

The current git page suggests starting using the command "pip install fontmake" This failed for me because it didn't set up the python support or the virtual environment that seems to be the preferred method of using fontmake as of now.

I was fortunate to get some help from Stephen Nixon and this is what worked for me instead. Some of this is just checking and isn't essential but I include it here especially to help people like me that are still a bit new to terminal commands etc.

Note: If I get some of the explanations mixed up I hope Stephen will help me correct it! :

1) First we moved the place the terminal pointed to to my user dir using a series of `cd ..` commands
2) Then we used the command `mkdir virtualenvs` Note: this is just a dir to put instances of virtual environments in - hence the plural name.
3) Then` ls` so we could see that the dir was there
4) Then into the new folder or dir `cd virtualenvs`
5) Then we checked the version of virtualenv I had installed already `virtualenv --version`
6) Then we installed the python we wanted `virtualenv -p python3`
7) Then we made new environment to test that we could make new standalone project environments `virtualenv -p python3 TestEnv`
8) We checked that the new dir was made `ls`
9) We then went into that dir `cd TestEnv`
10) Checked contents of the dir `ls`
11) Opened a finder window showing the contents `open .`
12) Moved back out to the "virtualenvs" directory `cd ..`
13) Entered and Activated the virtual environment `TestEnv/bin/activate`
The terminal now lists the bash with the text (TestEnv) to start indicating we are in and using this Virtual Environment
14) Installed fonttools `pip install fonttools`
The success is reported "Successfully installed fonttools" ( Normally silence or no message indicates success )
15) We used TTX to convert a TTF file which was done by typing` ttx` a space and then dragging the file to the terminal to indicate the path to the file. This happened to look like this afterwards` ttx /Users/ebensorkin/Library/Fonts/Merriweather-Regular.ttf
16) With that done we deactivated the virtual env `deactivate`
17) Then we made a new Virtual environment meant to be used specifically for the Merriweather Serif project and to remind me that you can do this. `virtualenv -p python3 TestMerriweather`
18) Then we activated the new virtual env `TestMerriweather/bin/activate`
19) Then we installed fontmake `pip install fontmake`
20) A great deal of activity followed including Installing collected packages: lxml, appdirs, pytz, six, fs, fonttools, defcon, glyphsLib, compreffor, pyclipper, booleanOperations, cu2qu, ufo2ft, fontMath, MutatorMath, fontmake after which we listed the commands for this `fontmake --help`
21) Then we tested making a Variable Font with Fontmake from a Glyphs file source `fontmake -o variable -g`

There were problems we found and we fixed some of them today but this post is about how to get running not the problems of my Glyphs file!

I suspect that having a contemporary copy of virtualenv and pip running are probably key. I am not able to advise about this and hope Stephen or others will chime in on this subject!