Coerce user attributes to strings before checking that they are valid.

If the user attributes were defined as symbols, the validation would fail as it was expecting strings.
Merge pull request #211 from cgunther/user-attribute-symbol-warning

Coerce user attributes to strings before checking that they are valid.
Reject invalid user attributes on assignment

Invalid user attributes cause XML that the server cannot process, so they should be rejected on assignment, in addition to the warning that is already provided.
Merge pull request #212 from cgunther/exclude-invalid-user-attributes

Reject invalid user attributes on assignment
Allow backtrace to be a String
add test for warnings about user attributes
remove unnecessary active record requirements
use 'bundle exec' in capistrano task
remove platform checks from nil logger initialization
update bourne dependency to fix test-running issues with ruby 2.0.0

bourne is dependening on mocha that had issues with ruby 2.0.0 in its
older versions. this commit updates bourne to a newer version, which
resolves the test-running issues
test against ruby 2.0.0 on a CI server
remove mocha deprecation warnings
be more careful when reading sinatra environment name

closes #202
split javascript notifier into loader and configuration

Conflicts:
	lib/airbrake/rails/javascript_notifier.rb
	lib/templates/javascript_notifier
	lib/templates/javascript_notifier.erb
	lib/templates/javascript_notifier_configuration.erb
wrap the js configuration in try-catch
return environment_info unless environment_name

return environment_info if configuration.environment_name dose not exists. (plain ruby script)

```
def foo
  info = 'first'
  info << ' second' if false
end

foo
=> nil

def foo
  info = 'first'
  info << ' second' if false
  info
end

foo
=> 'first'
```
Merge pull request #217 from ZubKonst/patch-1

return environment_info unless environment_name
Escape user name in Airbrake notify command

If a user has manually overridden this variable to be a full name, it
may contain a space which will break the command. Escaping the name
solves this issue.