Remove obsoleted TcpInput

StreamInput based TcpInput is obsoleted since 2+ years ago.
So we can remove this class for newer plugin
Add udp input plugin
Add tcp input plugin
in_syslog uses socket utility handlers instead of own handlers
add time_default_current (default true) to disable filling current time when time is not produced by parser result
Add config_param "time_default_current" not to set current time into parse result
 * By setting current time, caller cannot know "time" is from whether parse result or current time
   * it brings troubles especially in case for filter plugins like fluent-plugin-parser
 * naming problem:
   * 'time_' prefix seems important for me
Remove trailing delimiter on both udp and tcp
Fix feature from config_param to attr_accessor
 * not to be enabled on plugin direct use
Add other format tests to udp and tcp inputs
for clear code
add comment for implement restrictions
fix configuration parameter name for readability
Merge pull request #368 from fluent/add-udp-tcp-input

Add udp and tcp input
fix tests with current code
Merge pull request #370 from tagomoris/parser_default_current_time

Add "estimate_current_event" attribute to TextParsers not to set current time into parse result
Add SyslogParser and replace broken syslog parser
Use SyslogParser instead of own regexp parser
Add with_priority parameter to support both packet and file formats
Fix rotated handling when new file not found
Add test-case for file rotation