Do not encode the entire URL, only the job name
Store triggered build environment variables

Save TRIGGERED_BUILD_NUMBER and, if blocking, TRIGGERED_BUILD_RESULT to
the build environment. Prior to this change, it was necessary to parse
the log file, which was very hacky and only possible on the master. This
can be used by later build steps and downstream jobs.
Validate build number by reading parameters

If multiple jobs are started at the same time, it can be challenging to
determine the correct build numbers for each, as Jenkins does not
respond with the build number. To help mitigate this risk, check the
expected build parameters, and if they do not match then scan +-2 build
numbers looking for the correct build.
Merge pull request #5 from scottanderson/master

Multiple bug fixes