Changed the psycopg2 install method for Windows.

The current suggested method relies on git being installed
on the user's machine.
This new one is slightly more complex (there's an
extra step of downloading a prebuilt binary) but
it should work with nothing else installed.
Explain how to add Postgres to PATH on OS X
All codes are working.

* cleanup in codes

* some explanations and hints for some troubleshooting
Removed redundant info about installing psycopg2
Some more native speaker proofreading

Gave the 'database', 'code editor', 'Django installation' and 'Start a Django Project' pages a quick linguistic overhaul.
Merge pull request #30 from foonicorn/features/osx_postgres_path

Explain how to add Postgres to PATH on OS X
Resolved conflicts
Merge branch 'mcmillan-master'
resolved conflicts
Merge branch 'bmispelon-psycopg2-win-altinstall'