Test android project

[JinneeJ]

This PR contains basic Android project to test compatibility of commonmark-java on Android with SDK version >= 15.

Also was added README for commonmark-android-test with instructions and links :)

Currently autolinkExtensionTest fails for SNAPSHOT because of Objects. There are 2 options: deleting test of autolink or adding android support to autolink :)
All tests for current maven version fail - as expected.

Also was fixed SpecReader since android tests use the spec.

[robinst]

Wow, this looks great 😃! I'll try to look into how we can use Travis or some other CI solution to include this in the build, hopefully soon.

For autolink, does this fix the problem?: robinst/autolink-java@a8e85e3

[JinneeJ]

It looks that this change will fix the problem :)

[robinst]

Released a new version of autolink-java and bumped it on master. Can you check if it works?

Also started trying to make the build on Travis work on the test-android-project-travis branch. It currently fails. Here's the result I get, any ideas what the problem could be?:

https://travis-ci.org/atlassian/commonmark-java/jobs/108276173

commonmark-android-test/app/build.gradle' line: 44

I'll try turning on some more debugging later.

[JinneeJ]

Autolink
With new autolink-java all tests are passed 👍

Travis
It seems that you don't create test.properties. May be it will work after adding to .travis.yml something like that:

...cd commonmark-android-test
&& touch ./test.properties
&& echo "path.report=../report" > ./test.properties
&& echo "version.maven=0.4.0" >> ./test.properties
&& echo "version.snapshot=0.4.1-SNAPSHOT" >> ./test.properties
&& echo "version.snapshot_autolink=0.4.0" >> ./test.properties
&& ./gradlew :app:connectedSnapshotDebugAndroidTest; fi

Also if Travis doesn't support the launch of Android emulator then you need to add the launch of emulator to .travis.yml too (please see README)

[robinst]

Merged. I've done the Travis changes in a follow-up PR, see #40.