http support pprof and template add date func like php's date function

http support pprof
PprofOn set to true you can profile the runtime data.
template add date func like php's date function

{{date "Y-m-d H:i:s"}}
add session support
fix session's maslifetime bug
refactor: use switch instead of if/else to select ProfController type
Merge pull request #5 from corburn/master

Refactor pprof.go to use switch instead of if/else
add TemplateCache
fix a bug about json and xml
removed  trace for merging
basic authentication function