Merge pull request #14 from tsuzakiyo/master

ap_mrb_init.c, ap_mrb_request.h and ap_mrb_request.c modified
proxy functions added.
reverse-proxy sample added.
proxy.mrb changed.
sample vhost.mrb added.
headers_out beta added.
BETA headers_in headers_out implemented.
support apache 2.4.

if you use apache 2.4 settings, you will delete APXS APACHECTL DEF comment for apache 2.4.
Apache 2.4 supported and loglevel fixed.
mrb_parser_file args changed.
require deleted on README.
require deleted on sample scripts.
headers_in headers_out class created.

h = Apache::Headers_in.new()
Apache.rputs(h["Accept-Encoding"] + "<BR>")
h["Accept-Encoding"] = "gzip"
test script created.
test.mrb modified.
a little fix.
mod_mruby_version method created.
version 0.2.1 -> 0.3.1
Apache 2.4 log.level supported.
AUTHORS created.