subroutines for additional url parameter "repo_id"

if a specific repository id is passed in url parameter "repo_id", then
try to find it in the list of current project repositories and use only
this and not all to pull changes from (fixes issue #54)
Logging info for which repos have been updated
indent other log messages
add profiling/debug info in log about how long the fetch and redmine import commands have taken
 updated README.md to reflect new plugin behavior
Merge pull request #58 from tofi86/feature/update-repo-from-url-param

Feature/update repo from url param
Clean up formatting
Move business logic out of the controller
Test the Updater directly instead of via the controller
Converting inputs to something usable belongs in the controller

This includes parsing the JSON payload into a Ruby hash that we can use in the
updater.
Only log if a logger is given
Spell out the repository_id parameter
Adds specs for updating just a specific repository
Remove unused code
Bump version