Migrate from TravisCI to CircleCI (#92)

* Migrate from TravisCI to CircleCI.
* Use prepared Docker build environment.
* Update build badge.

.circleci/Dockerfile

@@ -0,0 +1,14 @@
+# To build and publish image run following commands:
+# > docker build -t cahirwpz/amigaos-cross-toolchain-buildenv:latest .
+# > docker login
+# > docker push cahirwpz/amigaos-cross-toolchain-buildenv:latest
+
+FROM debian:jessie
+
+WORKDIR /root
+
+RUN apt-get -q update && apt-get upgrade -y
+RUN apt-get install -y --no-install-recommends \
+            git-core make gettext patch bison flex gperf ca-certificates \
+            gcc g++ gcc-multilib libc6-dev libncurses-dev \
+            python2.7 libpython2.7-dev python-setuptools

.circleci/config.yml

@@ -0,0 +1,35 @@
+version: 2
+
+defaults: &defaults
+  working_directory: ~/amigaos-cross-toolchain
+  docker:
+    - image: cahirwpz/amigaos-cross-toolchain-buildenv:latest
+
+jobs:
+  m68k:
+    <<: *defaults
+    steps:
+      - checkout
+      - run: './toolchain-m68k --quiet build'
+      - store_artifacts:
+          path: m68k-amigaos
+      - save_cache:
+          key: m68k-amigaos-{{ .Branch }}-{{ .Revision }}
+          paths: m68k-amigaos
+
+  m68k-tests:
+    <<: *defaults
+    steps:
+      - checkout
+      - restore_cache:
+          key: m68k-amigaos-{{ .Branch }}-{{ .Revision }}
+      - run: './toolchain-m68k --quiet test'
+
+workflows:
+  version: 2
+  amigaos-cross-toolchain:
+    jobs:
+      - m68k
+      - m68k-tests:
+          requires:
+            - m68k