Mix vimrc with syntastic

1. Register javascript, python, php checker to syntastic
2. Keybinding for triggering Syntastic
3. Change keybinding commands for disabling nested mapping
Better experiences on syntastic

1. Combine on-off syntastic checking feature in one button.
2. Remove jshint2 plugin since the existence of syntastic.
3. Change default errors colors highlight on syntastic for readability.
4. Change error symbols for readability purpose
5. More hotkeys for navigate errors on location-list