Use 1.4.1 of pip.

- This is where the option pip install --pre is.

Change-Id: I3f836a701f17a4fea888ec51da62e7137cf0e6db
diff --git a/tools/install_pip.sh b/tools/install_pip.sh
index 6e3e9d2..cb414a7 100755
--- a/tools/install_pip.sh
+++ b/tools/install_pip.sh
@@ -25,7 +25,7 @@
 
 # Handle arguments
 
-INSTALL_PIP_VERSION=${INSTALL_PIP_VERSION:-"1.4"}
+INSTALL_PIP_VERSION=${INSTALL_PIP_VERSION:-"1.4.1"}
 while [[ -n "$1" ]]; do
     case $1 in
         --force)