BREAKING CHANGE: Delta Pager + Large Refactor (#43)

BREAKING CHANGE: This MR addresses an underlying issue with the original implementation in regards to detecting line numbers for comments. 

As such, this is a major breaking change. The setup function signature has changed, please review the `README.md` for the new arguments. The delta pager has also been added as a dependency: https://github.com/dandavison/delta

There will be future work to implement a native solution for parsing changes and line numbers.

lua/gitlab/reviewer/init.lua

@@ -0,0 +1,36 @@
+-- This Module will pick the reviewer set in the user's
+-- settings and then map all of it's functions
+local state = require("gitlab.state")
+local delta = require("gitlab.reviewer.delta")
+
+local M = {
+  reviewer = nil,
+}
+
+local reviewer_map = {
+  delta = delta
+}
+
+M.init = function()
+  local reviewer = reviewer_map[state.settings.reviewer]
+  if reviewer == nil then
+    vim.notify(string.format("gitlab.nvim could not find reviewer %s", state.settings.reviewer), vim.log.levels.ERROR)
+    return
+  end
+
+  M.open = reviewer.open
+  -- Opens the reviewer window
+
+  M.jump = reviewer.jump
+  -- Jumps to the location provided in the reviewer window
+  -- Parameters:
+  --   • {file_name}      The name of the file to jump to
+  --   • {new_line}  The new_line of the change
+  --   • {interval}  The old_lien of the change
+
+  M.get_location = reviewer.get_location
+  -- Returns the current location (based on cursor) from the reviewer window
+end
+
+
+return M