don't clean .idea directory.
shinkenplugins: give output on assert. + get early sys.args if none explicitely given.
pip install -r requirements.tests.txt if it exists.
imported arprequest from PyPI.
Adapted arprequest.
arp_no_change: Added files and implemented first "basic" check.
Moved arprequest body into check_arp_no_change.
arp_no_changed: implemented a simpler version using /usr/bin/arp tool.
added symbolic link
add .py extension to script
check_arp_no_change: partially rewrote + begin tests.
check_arp_no_change: Implemented even more and better tests and slightly changed check_arp_no_change.
Merge branch 'check_arp_no_change'