Add note about updating system path

Remind users to update system path since script does not. 

Well, at least on Windows it doesn't update PATH. Perhaps this should be qualified?
Merge pull request #1888 from patricktokeeffe/patch-1

Add note about updating system path
get-pip.py option examples

Conflicts:
	docs/installing.rst
break out the examples so we can add a qualifying footnote for --user installs

Conflicts:
	docs/installing.rst
Merge pull request #1944 from qwcode/critical_get-pip_docs

docs for get-pip.py options
Replaces spaces in username.
Merge pull request #1986 from matham/master

Replaces spaces in username.
Revert "Merge pull request #1986 from matham/master"

This reverts commit cb26c0b8cb00d18c75503ce4ee59a95a619e8189, reversing
changes made to bb8c7428ab40dde4af92e696ff518e82e214cd24.
Merge branch 'develop'

Conflicts:
	docs/installing.rst
	docs/reference/pip_install.rst
Ensure that we preserve executable file permission bits