add usage function for contrib/stylechecker.py.
merged changes between nginx 1.4.7 and 1.6.1 except spdy
updated testcases
Merge pull request #517 from cfsego/merge-nginx-1.6.1

merged changes between nginx 1.6.1 and 1.4.7
dynamic_resolve.t: skip cases without Net::DNS::Nameserver
SPDY: fix connection leak

 * If ngx_http_spdy_finalize_connection() was called,
   ngx_http_spdy_body_filter(r, in) should return NGX_ERROR.
 * The write timer of spdy connection may be deleted.
Merge pull request #527 from chobits/spdy_bugfix

SPDY: fix connection leak
Merge pull request #526 from chobits/master

dynamic_resolve.t: skip cases without Net::DNS::Nameserver
upstream rbtree bugfix(issue #530)
Merge pull request #531 from taoyuanyuan/rbtree

upstream rbtree bugfix(issue #530)
Merge pull request #513 from soarpenguin/master

add usage function for contrib/stylechecker.py.