Move travis from Ubuntu to docker+openSUSE

Travis supports only quite old Ubuntu releases.
They don't ship with libsignal-protocol-c and not with a recent enough
libgrcypt.
We could build libsignal-protocol-c manually but for libgcrypt it's more
annoying.
Let us switch to Docker and use openSUSE Tumbleweed, which is rolling
release) and thus have up to date libs.

Dockerfile

@@ -0,0 +1,46 @@
+# Build the latest openSUSE Tumbleweed image
+FROM opensuse/tumbleweed
+
+RUN zypper --non-interactive in --no-recommends \
+  git \
+  gcc \
+  autoconf \
+  autoconf-archive \
+  make \
+  automake \
+  libtool \
+  glib2-devel \
+  gtk2-devel \
+  libXss-devel \
+  libcurl-devel \
+  libexpat-devel \
+  libgpgme-devel \
+  libmesode-devel \
+  libnotify-devel \
+  libotr-devel \
+  libuuid-devel \
+  libcmocka-devel \
+  ncurses-devel \
+  python3-devel \
+  python3 \
+  python-devel \
+  python \
+  readline-devel \
+  libsignal-protocol-c-devel \
+  libgcrypt-devel \
+  libmicrohttpd-devel
+
+RUN mkdir -p /usr/src
+WORKDIR /usr/src
+
+RUN mkdir -p /usr/src/stabber
+RUN git clone git://github.com/boothj5/stabber.git
+WORKDIR /usr/src/stabber
+RUN ./bootstrap.sh
+RUN ./configure --prefix=/usr --disable-dependency-tracking
+RUN make
+RUN make install
+
+RUN mkdir -p /usr/src/profanity
+WORKDIR /usr/src/profanity
+COPY . /usr/src/profanity