Merge pull request #4 from Ruiyun/master

true multi-thread test passed.
add return value to the tree
pr-str the return value
fix issue #6

When there exceptions are thrown, reset level to 0
clean up the code
use a atom to store the wrapped function to original function mapping
fix issue #5
cleanup code
minor
objects should be only traced once
add color print
switch on color print, user can use set-color-print-on! and
set-color-print-off! to control if printting in color.

It's true on defalt.
make it false by default
make it works like :show-tid, without a globle switch. to turn color print off, user have to untrace a ns and then trace without :with-color flag. This seems not so convenient as a global switch. Which one do you preffer?
Merge pull request #9 from qiuxiafei/master

add color print
Update contributors
Correct a name.
style fixes
use colorize
Merge pull request #10 from Bronsa/master

Style fixes & switch to colorize