[Feature Addition] Added Pastebin upload feature

User can now choose to upload the generated file to pastebin. Obviously,
the user needs to enter his pastebin dev key once after which it will be
locally stored on his machine.

Signed-off-by: Siddharth Goel <siddharth98391@gmail.com>
Updated .gitignore

Modified .gitignore to ignore the .pastebin-devkey file which stores the
user's pastebin api dev locally.

Signed-off-by: Siddharth Goel <siddharth98391@gmail.com>
Updated README.md

Signed-off-by: Siddharth Goel <siddharth98391@gmail.com>