indent for map/exe commands to make code more readable
add mapping to show python module source code directly
modify settings for signify plugin

1. change difftool to vimdiff
2. change colors for signify
add the filetypes utilizing indentline plugin
change python snippets

change python environment from ipython to python3
add more snippets for python

1. for python: exception
2. for python: elif (else if)
add misc plugins' dependency info
add tuning plugins info