Integrated with new dropsonde changes

[mrbuk]

With current PCF version 1.6 the snotel library runs into some problems because the http.proto has now more METHODs. Also other changes to dropsonde architecture have been done the following has been done to reflect that:

• bumped version to 0.4-SNAPSHOT
• added newest dropsonde protocol version (git submodule magic)
• removed ControlMessage and Heartbeat as described in https://www.pivotaltracker.com/n/projects/993188/stories/96706488 and https://github.com/cloudfoundry/dropsonde-protocol/commit/6a986020f511f4a8571b6265b7df37b2c671fe02
• refactored code to use new dropsonde java package name
• bumped 'wire' version to 2.2.0 to be able to work with map structure in envelope.prot (see https://github.com/cloudfoundry/dropsonde-protocol/commit/74d3c2d919a37a10dd264704903d46a89ac0c28c)

[youngm]

Wire 2.2.0 supports Map? Excellent!