Remove unused gems, update berkshelf/chefspec/rspec and unconstrain rubocop

Before:
```
ChefSpec Coverage report generated...

  Total Resources:   119
  Touched Resources: 109
  Touch Coverage:    91.6%

Untouched Resources:

  link[/usr/lib/hive/lib/mysql-connector-java.jar]   hadoop/recipes/hive.rb:61
  link[/usr/lib/hive/lib/postgresql-jdbc.jar]   hadoop/recipes/hive.rb:61
  directory[/tmp/${user.name}]       hadoop/recipes/hive.rb:88
  template[/etc/hive/conf.chef/hive-site.xml]   hadoop/recipes/hive.rb:100
  execute[hive-hdfs-warehousedir]    hadoop/recipes/hive_metastore.rb:56
  directory[/tmp]                    hadoop/recipes/hive.rb:88
  link[/usr/lib/hive/lib/postgresql-jdbc4.jar]   hadoop/recipes/hive.rb:61
  log[hdp-2.1 release engineering fix]   hadoop/recipes/zookeeper_server.rb:143
  directory[/usr/lib/bigtop-utils]   hadoop/recipes/zookeeper_server.rb:147
  file[/usr/lib/bigtop-utils/bigtop-detect-javahome]   hadoop/recipes/zookeeper_server.rb:150
```

After:
```
ChefSpec Coverage report generated...

  Total Resources:   119
  Touched Resources: 112
  Touch Coverage:    94.12%

Untouched Resources:

  directory[/tmp/${user.name}]       hadoop/recipes/hive.rb:88
  template[/etc/hive/conf.chef/hive-site.xml]   hadoop/recipes/hive.rb:100
  execute[hive-hdfs-warehousedir]    hadoop/recipes/hive_metastore.rb:56
  directory[/tmp]                    hadoop/recipes/hive.rb:88
  log[hdp-2.1 release engineering fix]   hadoop/recipes/zookeeper_server.rb:143
  directory[/usr/lib/bigtop-utils]   hadoop/recipes/zookeeper_server.rb:147
  file[/usr/lib/bigtop-utils/bigtop-detect-javahome]   hadoop/recipes/zookeeper_server.rb:150
```