Updated various links in docs to avoid redirects

Thanks Tim Graham and Mariusz Felisiak for review and completion.

docs/ref/contrib/gis/install/index.txt

@@ -257,7 +257,7 @@ Summary::
     $ brew install gdal
     $ brew install libgeoip
 
-__ http://brew.sh/
+__ https://brew.sh/
 .. _Xcode: https://developer.apple.com/xcode/
 
 .. _kyngchaos:
@@ -402,8 +402,8 @@ install :ref:`postgisasb`.
     and contains shortcuts for the ASB as well as the 'SQL Shell',
     which will launch a ``psql`` command window.
 
-__ http://www.enterprisedb.com/products-services-training/pgdownload
-__ http://www.enterprisedb.com
+__ https://www.enterprisedb.com/downloads/postgres-postgresql-downloads
+__ https://www.enterprisedb.com
 
 .. _postgisasb:
 

docs/ref/contrib/gis/install/spatialite.txt

@@ -133,4 +133,4 @@ following to your ``settings.py``::
 
     SPATIALITE_LIBRARY_PATH='/usr/local/lib/mod_spatialite.dylib'
 
-.. _Homebrew: http://brew.sh/
+.. _Homebrew: https://brew.sh/