Add support for vim-latex, and cleanup Makefile

Lines should end with a newline character, see https://stackoverflow.com/questions/729692/why-should-files-end-with-a-newline and https://stackoverflow.com/questions/5813311/no-newline-at-end-of-file .

Define phony targets, see https://stackoverflow.com/questions/2145590/what-is-the-purpose-of-phony-in-a-makefile .

A user requested to add a `pdf` target because this is used by vim-latex to compile the document. The file `main.tex.latexmain` is used by vim-latex to determine which document is the master document of the project.