* Fix deploy conditions in CI script

The deploy conditions had been using a powershell-only variable, and not a environment variable. This meant that the deployment failed on both Windows and Linux (expected only on Linux).

* Remove an extra newline

* Remove Debug statements from appveyor build script

* Target Ubuntu in Appveyor CI build

AppVeyor has released support for targetting Ubuntu 18.04 environments.
This adds Ubuntu to the list of build images for Appveyor to use.

* Set clone folder to use appveyor defaults

* Check if appveyor provides appveyor-retry by trying to run it

* Minor syntax change

* Minor syntax change

* Skip using appveyor-retry (for now)

* Use forward slash for paths so that it works on both windows and linux

* Implement replacement for appveyor-retry

* Script cleanup

* Remove commented out line

* Only package releases on Windows

* Add the isWindows condition to the deploy stage

this was the name change i always wanted

This adds the following property to ITextChannel
- SlowMode (int)

The SlowMode field defines the time in seconds users must wait between
sending messages; if zero, slow-mode is disabled.

Bots are not affected by slow-mode, and as such, no changes need to be
made to the REST client's internal ratelimiting. This is strictly a
read/write cosmetic property for bots.

* Fix swapped parameters in ArgumentException and ArgumentNullException cstrs

The constructors of ArgumentException and ArgumentNullException are inconsistent with each other, which results in their parameters being swapped here and there.

* Use named parameters for ArgumentException constructors

Cleans up some of the methods of EmbedBuilder to use simpler syntax as well

+ Add introductory paragraphs to each FAQ section.
+ Add 'missing dependency' entry to commands FAQ.
* Split commands FAQ to 'General' and 'DI' sections.

+ This commit reflects the new changes made to the Discord Application Developer Portal after its major update

This commit rewrites the remarks section of GetMessagesAsync, as well as adding examples to several methods.

+ Geez, I didn't know there were so many.

+ Original lines stated that sending a emoji wrapped in colon will not be parsed, but that was incorrect; replaced with reactions instead of sending messages as the example

* Change all Select(... as ...) to OfType

* Add changes according to 194a8aa427

* Add input validation for bot tokens based on their length

* Add token validation to BaseDiscordClient#LoginAsync

Adds a TokenUtils class which is used to validate that tokens are correct

* Revert changes to DiscordRestApiClient

* Add Unit tests to the TokenUtils class, fix a logic error that was caught by those tests

* Allow for API to throw exceptions

Moves the validation of tokens to be inside of LoginInternalAsync, and writes a Warning to the console when the supplied tokens are invalid

Should fix issues in audit logs when deserializing overwrites and
similar types which we use a custom contract resolver for.

Nullable<T> is not valid for Attributes, this is my suggested fix.

* Initial commit

* Add alternative suggestion

* Fix typo

* Update README.md