On branch master

 Changes to be committed:
	modified:   vimrc
	modified:   vimsetup.sh
	modified:   zshrc

Summary of changes:
    * Added try/catch/endtry to vimrc to suppress error message about a plugin that hasn't had the chance to be installed yet.
    * Changed function names in vimsetup to make them more clear in their role.
    * Added cmd_exists() to support dependency checking refactoring.
    * Renamed chkdep() to main() and made calls to cmd_exists() in the for loop as part of the refactoring.
    * install_deps() function will determine the OS and package manager by proxy for use in installing any missing packages found by cmd_exists().