Changed Travis build file to use Android API 10 and Android build tools 18.1.1

This is a trivial change, but I wanted to explain it a bit.

I forked the repo to try a few things out on Travis on my own without spamming everyone with 'build failed' emails.  I tried at first to update the sdk with API 10 as such:
```
echo yes | $ANDROID update sdk --filter 1,2,3,14 --no-ui --force > log.txt
```
But as I suspected, the build failed as described in issue #567.  I fixed that by adding the -a switch (read: 'all') to be able to access the 18.1.1 android build tools.

P.S.
Sorry about the commit author as RyanInspiratica.  That is an old work account that I apparently forgot to change.