Error with jarfile sbt-launch-0.13.7.jar

Hello,

The script `build/sbt-launch-lib.bash` doesn't correctly download the file `sbt-launch-0.13.7.jar`. As a result, we get the error while trying to compile with `./build/sbt compile`:
> Error: Invalid or corrupt jarfile build/sbt-launch-0.13.7.jar

[This solution found in StackOverflow](http://stackoverflow.com/a/31848979) works. I reproduce here the change to be done to lines 53-57 for the download to correctly complete.

```
if hash curl 2>/dev/null; then
(curl --fail --location --silent ${URL1} > ${JAR_DL} ||\
(rm -f "${JAR_DL}" && curl --fail --location --silent ${URL2} > ${JAR_DL})) && \
mv "${JAR_DL}" "${JAR}"
elif hash wget 2>/dev/null; then
(wget --quiet ${URL1} -O ${JAR_DL} ||\
(rm -f "${JAR_DL}" && wget --quiet ${URL2} -O ${JAR_DL})) &&\
mv "${JAR_DL}" "${JAR}"
else
```