Merge pull request #1 from xiangli-cmu/master
add name field to fix #1
add error string
switch license to Apache v2 to fix issue #2
change fields function to return interface{}
add formator
link formater and fields to the logging system
fix formater wrong
using a log struct to store each log
fix richformat error
move calldepth value to the genRuntime function
errorString -> errString
generate short function name
use goroutine for file writing, rather than others

this makes the system able to generate runtime information
revise fields_test based on the API changing in fields.go
delete module name from richformat
fix typo
clean code
use path.Base instead of parsing string
clean code