fix buffer configurations

fix buffer configurations such as:
 * specified in out_webhdfs.rb
   * buffer_type memory
   * buffer_path must be specified for `buffer_type file`
 * TimeSlicedOutput default options
   * flush_interval nil
   * buffer_chunk_limit 256m
 * buf_memory's default options:
   * buffer_queue_limit 64

Are these descriptions copy&past-ed from out_exec_filter's documents?
(originally `flush_interval 1s`)
Merge pull request #9 from tagomoris/patch-1

fix buffer configurations
updated docs for TimeSlicedOutput
enable PrechatSurvey for olark
prechat survey config can be done on the server side
edit %Y description: out_file.txt
edit %Y description: out_s3.txt
add faq on windows
Improve style: faq.txt
rack security fix

@see https://support.cloud.engineyard.com/entries/23128893-February-8-2013-Rack-Vulnerability
Grammar fixes for recent output plugin document updates
Improve style: toc.rb
fixed typo.
Merge pull request #11 from chocoby/fix_typo

fixed typo.
ruby v2.0.0
add slide from masa
improve style: slides.txt
explicitly say fluentd doesn't run on windows
testimonial from @pitr
people often ask about support...