S:change spell checking shortcut

W:change spell checking short cut from <leader>ss to <leader>sc
to avoiding confliction between fugitive#statusline

[ticket:X]
S:root cause found on fugitive#statusline

W:not confliction between <leader>ss, but need seperate source $MYVIMRC
in otherwords, need rerun the status line setting

[ticket:X]
S:mannually source .vimrc

W:source vimrc to udpate statusline

[ticket:X]
S:install gundo and lightline

W:fix fugitive statusline issue. and enhanced with gundo to work with git

[ticket:X]
S:resolve confliction between LookupFile and gundo

W:F5 is already been used by LookupFile
change F5 to F4 for trigger gundo

[ticket:X]