added 1.8.1-pre-release test builds

Also added requests to pip install list

Change-Id: Ic8b405e28a03e6b5615f1651fd46081c79f7bf9e
Reviewed-on: http://review.couchbase.org/19226
Reviewed-by: Benjamin Young <benjamin@couchbase.com>
Tested-by: Benjamin Young <benjamin@couchbase.com>

.travis.yml

@@ -10,6 +10,7 @@ branches:
 
 env:
   - CB_URL="http://packages.couchbase.com/releases/1.8.0/couchbase-server-community_x86_1.8.0.deb" CB_DEB="couchbase-server-community_x86_1.8.0.deb" CB_VER="1.8.0"
+  - CB_URL="http://builds.hq.northscale.net/latestbuilds/couchbase-server-community_x86_1.8.1-916-rel.deb" CB_DEB="couchbase-server-community_x86_1.8.1-916-rel.deb" CB_VER="1.8.1"
   - CB_URL="http://packages.couchbase.com/releases/2.0.0-developer-preview-4/couchbase-server-community_x86_2.0.0-dev-preview-4.deb" CB_DEB="couchbase-server-community_x86_2.0.0-dev-preview-4.deb" CB_VER="2.0.0"
 
 python:
@@ -24,6 +25,6 @@ before_install:
   - cp test.ini.template test.ini
 
 install:
-  - pip install nose-testconfig coverage
+  - pip install nose-testconfig coverage requests
 
 script: nosetests --tc-file=test.ini --with-coverage --cover-package=couchbase --cover-html -A "(cbv <= \"${CB_VER}\")"