update setup.py

call load_dot_env_file when initializing HttpRunner

bugfix httprunner#210: SuiteNotFound

release 1.4.0

merge_validator: support checking unhashable values such as dict

fix httprunner#188: display response image in html report

filter output if out is empty

fix httprunner#155: XSS in Jinja2 rendering

bugfix: when variable reference in testcase name is extracted from fo…

…rmer testcase, exception will occur

fix httprunner#131: parameter data driven with pair keys