Update build files

.travis.yml

 dist: trusty
 
 go:
-  - "1.9.x"
-  - "1.10.x"
+  - "1.11.x"
   - master
 
 before_script: make prepare
   - make critic
   - make test
 
-cache:
-  directories:
-    - vendor
-
 matrix:
   allow_failures:
     - go: master

Dockerfile

 ###############################################################################
 # BUILD STAGE
 
-FROM golang:1.10-alpine
+FROM golang:1.11-alpine
 
 RUN set -x \
   && apk --no-cache --update add \
     upx \
   && update-ca-certificates
 
-COPY Gopkg.toml Gopkg.lock Makefile /go/src/github.com/9seconds/mtg/
-
-RUN set -x && \
-  cd /go/src/github.com/9seconds/mtg && \
-  make -j 4 prepare && \
-  make vendor
-
-COPY . /go/src/github.com/9seconds/mtg
+COPY . /go/src/github.com/9seconds/mtg/
 
 RUN set -x \
   && cd /go/src/github.com/9seconds/mtg \