New dependency checking

[ESilva15]

Added an array with the dependencies binary names to check for.
Pros:

• Checking for a new dependency is as simple as adding it to the array;
• Throws all required dependencies at once. Otherwise one would have
  to install one dependency and see what else is missing and so on;
• Faster to read.
  Cons:
• Might be harder to read.

NOTE: sorry for the lack of history on this GitHub account, I deleted the older one.

[klaxalk]

Thanks, this is a great idea :-). One little remark: The original dependency check searched for vim or nvim. Now, it requires both. Could you please update your method (I don't have a tip now on how to do it in an elegant way)? I would do it myself, but I am currently a little busy. Thanks in advance!