Allow configuration of repository for user defined remote tasks

[iilyak]

Currently the repository is hardcoded here.

Which makes it hard for users to add own tasks. Currently the only ways to call remote tasks are:

• alfred iilyak/alfred-tasks - there is no way to select specific yml file

  ✘ https://raw.githubusercontent.com/iilyak/alfred-tasks/master/alfred.yml`
  

• alfred https://raw.githubusercontent.com/iilyak/alfred-tasks/master//testing.yml - very long

This problem could be solved either via:

• make the account name configurable (in the above mentioned line)
• inventing short syntax which includes user:
  • alfred iilyak/alfred-tasks:testing
  • alfred iilyak:testing
  • alfred iilyak/myrepo:testing - most flexible IMO