pushoverr 1.0.0

Reimplemented core functionality. No longer using S4 objects.
- Removed PushoverMessage and PushoverResponse classes
- Lots of source file reorganization
several functions have been deprecated
- cancel_receipt is deprecated in favor of cancel_retries
- is.valid_token is deprecated in favor of is.valid_app
- validate_key is deprecated in favor of verify_user
User/group and application keys are now stored in environment variables instead of a package-specific environment, which makes it easier to store keys in .Renviron
added support for the glances API (e.g., for smartwatches) via update_glance()
added is.valid_pushover_sound function to validate sound arguments
added get_pushover_limits function to retrieve application message limit and usage information
added stop_for_pushover_status to handle errors for all API requests
added functions for working with groups:
- get_group_info retrieves information about a group
- group_rename renames a group
- group_add_user and group_remove_user adds or removes a user from a group
- group_disable_user and group_enable_user temporarily disable and re-enable a user's group membership
Project now has a Contributer Code of Conduct

pushoverr 0.1.4

Added support for -2 priority messages ('silent'): http://updates.pushover.net/post/87000633097/api-change-to-message-priority-1-new-priority-2

Fixed small issue with user/token storage, which allowed similarly named variables outside the namespace to be used
pushover_* helper functions now return invisible values. Request tokens can still be saved to a variable, but will not be printed when the functions are not part of an assignment operation. The return values of pushover_high are visible.