Removing RestEasy dependency and adding jackson.

As far as I can tell there are now dependencies to RestEasy in the code
base. The dependency to RestEasy was of scope provided which meant that
a project depending on this one would have to define the dependency to
jackson them selves.

Adding jackson as a compile dependency allows project using this one to
not have to add any dependencies.
Switching to com.fasterxml.jackson.
Refactoring of SenderClient and JavaSender.
Merge branch 'dbevenius_work'
adding travis status icon
Updating dependency version desc.
[maven-release-plugin] prepare release 0.7.0
[maven-release-plugin] prepare for next development iteration
release time
Correct usage of Simple Sender creation
Remove redundant version declaration
Merge branch 'AGPUSH-783'
add action-category
renamed the argument
Merge branch 'AGPUSH-800'
Upgrade to AeroGear BOM 0.2.3
Merge branch 'bom-upgrade'
[maven-release-plugin] prepare release unifiedpush-java-client-0.8.0
[maven-release-plugin] prepare for next development iteration
Updating to 0.9.0