added the attribute 'id' for upstream server

This attribute can be specified by user. It may be useful for
session sticky load balance or other hash based methods.
merged changes between nginx-1.2.4 and nginx-1.2.5
added the attribute of id for round robin
initialized the id to be null string
updated the information of README.markdown
fixed the id prameter
Merge pull request #116 from zhuzhaoyuan/merge-nginx-1.2.5

merged changes between nginx-1.2.4 and nginx-1.2.5
cool！
Merge pull request #119 from zhuzhaoyuan/update-readme

updated the information of README.markdown
released Tengine-1.4.2
Merge pull request #122 from yaoweibin/tengine-1.4.2-2

released Tengine-1.4.2
remove unused variable in sysguard
bumped version
Merge pull request #124 from lifeibo/sysgurad_var

remove unused variable in sysguard
Merge pull request #125 from zhuzhaoyuan/bump-to-1.4.3

bumped version
fixed a segment fault bug with upstream check module when check timeout is longer than the check interval
change data type "ngx_int_t" to "int" to get rid of the compilation warning "comparision is always true".
removed the unnecessary parentheses
removed the macro NGX_HTTP_UPSTREAM_ID check expression
Merge pull request #129 from yaoweibin/fixed_check2

fixed a segmentation fault bug with upstream check module
Sysguard not work on mac os.