remove all deprecated functions
update readme
fix travis icon
support assignment operator
fix assignment operator
add assignment tests for Pipe object
update readme
refine utils
refine question mark feature
refine pipe function
use closure for Pipe
update info
use character to represent operator
make Pipe consistent with operator
update readme
implement #44
update manual (#44)
fix #45
fix #46
Use withVisible() in Pipe. Closes #48