Review changes for HTTP paths

This reviews the code and fixes up suggestions made by team for
the HTTP paths PR #789.

- Removed feature-flag (this is backwards-compatible, so I see
no value in adding the flag)
- There was a URL transform happening for calls proxied to the
back end, I changed this for the nil-transform - i.e. it does not
change anything in the URL
- Introduced variables to describe the regex indicies used in
the URL trimming.

Tested with Docker Swarm with a ruby-microservice, with
system calls and with function calls using the UI.

Signed-off-by: Alex Ellis (VMware) <alexellis2@gmail.com>

gateway/build.sh

@@ -19,7 +19,9 @@ if [ "$1" ] ; then
   fi
 fi
 
-echo Building openfaas/gateway:$eTAG
+NS=openfaas
+
+echo Building $NS/gateway:$eTAG
 
 GIT_COMMIT_MESSAGE=$(git log -1 --pretty=%B 2>&1 | head -n 1)
 GIT_COMMIT_SHA=$(git rev-list -1 HEAD)
@@ -28,4 +30,4 @@ VERSION=$(git describe --all --exact-match `git rev-parse HEAD` | grep tags | se
 docker build --build-arg https_proxy=$https_proxy --build-arg http_proxy=$http_proxy \
   --build-arg GIT_COMMIT_MESSAGE="$GIT_COMMIT_MESSAGE" --build-arg GIT_COMMIT_SHA=$GIT_COMMIT_SHA \
   --build-arg VERSION=${VERSION:-dev} \
-  -t openfaas/gateway:$eTAG . -f $dockerfile --no-cache
+  -t $NS/gateway:$eTAG . -f $dockerfile --no-cache