Use base64 encoding to support dump and import binary data

[gengmao]

Some of my zookeeper nodes have binary data. When I dumped them out and import back, I hit following exception.

ArgumentError: invalid byte sequence in UTF-8
         =~ at org/jruby/RubyRegexp.java:1657
     (root) at /home/mao/zookeeper-util/usr/share/zookeeper-util/bin/zk_import.rb:64
  each_line at org/jruby/RubyIO.java:3547
     (root) at /home/mao/zookeeper-util/usr/share/zookeeper-util/bin/zk_import.rb:63

Then I studied source code and #7, found the binary data was not processed correctly. As the dump file is only parsed as text file when import, the binary data need to be encoded in a revertible text format, for example base64.
With this PR, multi-lines node data can be imported too. Just one drawback - node data in the dump file are not readable any more.

[yongjunj]

@gengmao This worked like a charm - Thanks!

[19h]

I love you. Also, who cares if the data isn't readable anymore: I shat my pants when our dumps didn't import correctly.

🍻