fix log debug level detect
* reason
  there hardcodes DEBUG_LEVEL in logging.rb:
    DEBUG_LEVEL = defined?(Logger) ? Logger::DEBUG : 0
  this could cause some incompatibility between different logger tools

  for Logger, DEBUG/0 < INFO/1 < WARN/2 < ERROR/3 < FATAL/4,
  for Log4r,  ALL/0 < DETAIL/1 < DEBUG/2 < INFO/3 < WARN/4 < ERROR/5 < FATAL/6.

  anyway, it is not in good pattern.

* suggestion
  logger.debug { ... }
  if current level is greater than DEBUG, the block will not be
  evaluated. it is also efficient.

  following is also supported by most loggers.
  logger.info { ... }
  logger.warn { ... }
  logger.error { ... }
  ...
documentation improvements for Yard/Ydoc newbies, also relative links replace absolute links where possible so that the user is left with the exact version and not forced to current web docs, in accordance with DOCS-197
RUBY-442

Use read instead of readpartial.
Rescue ETIMEDOUT and raise appropriate ConnectionError
RUBY-437

Document batchSize better
Fixed a typo
Merge pull request #98 from ismell/patch-1

Fixed a typo
RUBY-435

Use rb_time_num_new for Time value when available (Ruby >= 1.9)
RUBY-442

Using sysread so Ruby 1.8.x won't complain about nonblocking IO#read
minor: testing fixes
minor: JRUBY hacks
minor: removing bson_ext from Gemfile
minor: authors++
b2json,j2bson: don't assume fixed ruby location
Merge pull request #100 from kzk/master

b2json,j2bson: don't assume fixed ruby location
RUBY-444 keep multiple replica set connections separate
Added BSON::ObjectId#to_ary
Fix copy-paste mistake in doc comment
Merge pull request #102 from balexand/patch-1

Fix copy-paste mistake in doc comment
minor: remove perftools
minor: rake task to compile and test c extension