Change Travis link in README.md

The old link pointed to https://travis-ci.org/excilys/androidannotations, which shows the last build. Since the last build can be a PR build, and not always the latest build on the develop branch, this can show misleading information about the project's status. Changed to https://travis-ci.org/excilys/androidannotations/builds, which shows the build history on the develop branch.
Removed http://githalytics.com from README.md

This site seems to be not working anymore.
Deprecate model parameter of @OrmLiteDao
Get model class from supertypes
Fix NPE during incremental build
Merge pull request #666 from yDelouis/289_modelOrmLiteDao

Remove model parameter from @OrmLiteDao
Updated gradle sample project
Merge pull request #1112 from WonderCsabo/1111_updateGradleSample

Updated gradle sample project
Building gradle sample in Travis build
Updated maven-android-plugin version

The previous version tried to resolved optional dependencies which
are no longer in Maven Central (namely android-rome-feed-reader).
The new version does not do this, so we can build without the
presence optional dependencies.
Merge pull request #1115 from WonderCsabo/gradleSampleTravis

Building Gradle sample in Travis