Prepering to support MAC:

UPDATED FUNCTIONS:
   * checkMD5sums2 - added "..."
   * check.for.updates.R - added a "pat" (pattern) parameter (this function might need more tweaking)
   * install.URL - moved to using "system" instead of "shell" (purpose - to allow the function to be useful for mac users as well.)

NEW FUNCTIONS ADDED:
   * up_folder - gets a vector of characters of folder paths, and returns them after turning them into a file.path once their tail was trimmed (through head(n = - 1).

OTHER NOTES:
   * moved to using "system" instead of "shell" (purpose - to allow the function to be useful for mac users as well.)
bug fix: install.Rtools - now returns FALSE gracefully if the user chooses to abort.