Move HTTP request onto its own thread

This avoids blocking app progress
Fix jruby specs
Wait for thread to finish
Add note about how to handle custom errors in Sinatra

The custom error handlers halt execution, so the error will not reach
Bugsnag.
Fix reference in readme
Merge pull request #122 from RKushnir/patch-1

Fix reference in readme
Merge pull request #121 from kytrinyx/document-sinatra-errors

Add note about how to handle custom errors in Sinatra
Update HC
Accept both String and Class instances as an ignored class.

If we accept actual Classes, developers can avoid typo-related
bugs if they so desire, e.g.:

```ruby
configuration.ignore_classes << "NotFoundEror"
 # => didn't catch a typo, sadface

configuration.ignore_classes << NotFoundEror
 # => Ruby will complain it can't find a constant
```
Merge pull request #119 from ecin/allow-non-string-ignored-classes

Accept both String and Class instances as an ignored class.
Check everything works
Use a queue instead

This makes it easier to see what's going on, and avoid problems
with booting up infinite threads.
Factor out queue into its own class

@kyrylo will be proud of me :)
Fix memoization
Merge branch 'threaded'
v2.2.0
Fix mixed up ENV revision/repository vars
bugsnag_generator: don't strip the initializer

Stripping removes trailing newlines. Git isn't happy about it.

  --- /dev/null
  +++ b/config/initializers/bugsnag.rb
  @@ -0,0 +1,3 @@
  +Bugsnag.configure do |config|
  +  config.api_key = <key>
  +end
  \ No newline at end of file
Merge pull request #124 from maxim/patch-1

Fix mixed up ENV revision/repository vars
Add endpoint docs to ruby notifier