Made DropSerializer test working.

Forgot how to use embedded classes...
remove unneeded imports
changed sourceCompatibility to 1.7
Added en- and decryption
Added test for en- and decryption
removed new byte[], use byteArrayOut/InputStream
Merge pull request #50 from jan-schreib/build.gradle

changed sourceCompatibility to 1.7
closes #2
Merge pull request #51 from roeslpa/basicSymmetricEncryption

Basic symmetric encryption
Added hybrid encryption and decryption method to CryptoUtils (encryptMessage and decryptMessage)
Merge pull request #52 from L-Henke/hybridEnc

Added hybrid encryption and decryption method to CryptoUtils
Added log4j 2.+ to build.gradle
Merge pull request #47 from jan-schreib/dropserializer-test-fix

Made DropSerializer test working.
combined symm dec and enc test
added .travis.yml

closes #13
Merge pull request #57 from jan-schreib/travis

added .travis.yml
trigger travis.
added travis picture
Merge pull request #56 from roeslpa/basicSymmetricEncryption

combined symm dec and enc test
Merge pull request #54 from L-Henke/log4j

Added log4j 2.+ to build.gradle
Added signature to encrypted messages.
Changed visibilities of methods in CryptoUtils.
Added log messages for (currently) unhandled exceptions.