Create a Makefile to make the life easy for newbies

[ryukinix]

From @ryukinix on February 1, 2018 23:51

The current build instructions is not great. Too many steps. make && make install is better.

Copied from original issue: #7

[ryukinix]

From @rafaelcn on February 2, 2018 0:15

To elaborate a little:

The current flow of the installation of xi-editor, the back-end, and xim, the front-end, is not so good. You have first to clone and install xi-editor with some three steps and some more to install syntax highlight, along with xim, which is approximately the same number of steps.
What we are thinking is:

1. Add xi-editor as a submodule to xim
2. Create a make that will make all of those steps in one make && make install.