Update dockerfile to add tzdata

Add tzdata so we can use the environment variable TZ to set a local timezone. Alpine lacks the package tzdata. Also bump version.

For more information about Alpine images:
gliderlabs/docker-alpine#136

Dockerfile

@@ -5,10 +5,10 @@ VOLUME /syncthing/config /syncthing/data
 CMD /start.sh
 ADD start.sh /
 
-ENV SYNCTHING_VERSION=0.14.46
+ENV SYNCTHING_VERSION=0.14.49
 
 RUN apk upgrade --no-cache \
- && apk add --no-cache apr apr-util ca-certificates su-exec xmlstarlet \
+ && apk add --no-cache apr apr-util ca-certificates su-exec xmlstarlet tzdata \
  && apk add --no-cache --virtual .build-deps apache2-utils curl tar \
  && cd /usr/bin \
  && cp htpasswd /tmp \