fixed bug with combiner and extra_files

Change-Id: I021d4cb5a2a49326e60c6179cf76106a33ea7497
Reviewed-on: https://gerrit.spotify.net/gerrit/47669
TC-Compile-And-Test: Team City <teamcity@spotify.com>
Reviewed-by: Elias Freider <freider@spotify.com>
Reviewed-by: Erik Bernhardsson <erikbern@spotify.com>
return stdout from call_check and use it in count() method

Change-Id: I9990e960582ad58e3e348ddc23a5c4ba05235346
Reviewed-on: https://gerrit.spotify.net/gerrit/48449
Reviewed-by: Elias Freider <freider@spotify.com>
adding hdfs put, get and getmerge methods

Change-Id: I9f905a391475435f0fc698368e3137d6cdbe7851
Reviewed-on: https://gerrit.spotify.net/gerrit/48531
TC-Compile-And-Test: Team City <teamcity@spotify.com>
Reviewed-by: Erik Bernhardsson <erikbern@spotify.com>