--user-data is broken if file contains non-utf-8 characters

[guss77]

Basically the same as issue #765 - after the fix, the file apparently can take UTF-8 encoded text files, but if I try to use a GZIP compressed file (because user-data is limited to 16KB, and compressing the data to workaround the limit is a valid practice and works great with the old Java based tools), then I get the following error:

'utf8' codec can't decode byte 0x8b in position 1: invalid start byte

[guss77]

Running with --debug:

2014-06-16 16:30:30,517 - MainThread - botocore.hooks - DEBUG - Event load-cli-arg.ec2.run-instances.UserData: calling handler <function uri_param at 0x7fccb2c1ade8>
2014-06-16 16:30:30,518 - MainThread - awscli.clidriver - DEBUG - Exception caught in main()
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/awscli/clidriver.py", line 191, in main
    return command_table[parsed_args.command](remaining, parsed_args)
  File "/usr/local/lib/python2.7/dist-packages/awscli/clidriver.py", line 338, in __call__
    return command_table[parsed_args.operation](remaining, parsed_globals)
  File "/usr/local/lib/python2.7/dist-packages/awscli/clidriver.py", line 443, in __call__
    self.arg_table)
  File "/usr/local/lib/python2.7/dist-packages/awscli/clidriver.py", line 470, in _build_call_parameters
    value = self._unpack_arg(arg_object, value)
  File "/usr/local/lib/python2.7/dist-packages/awscli/clidriver.py", line 486, in _unpack_arg
param, value)
  File "/usr/local/lib/python2.7/dist-packages/awscli/argprocess.py", line 66, in unpack_argument
    operation_name=operation_name)
  File "/usr/local/lib/python2.7/dist-packages/botocore/session.py", line 657, in emit_first_non_none_response
    responses = self._events.emit(event_name, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/botocore/hooks.py", line 148, in emit
    response = handler(**kwargs)
  File "/usr/local/lib/python2.7/dist-packages/awscli/argprocess.py", line 83, in uri_param
    return _check_for_uri_param(param, value)
  File "/usr/local/lib/python2.7/dist-packages/awscli/argprocess.py", line 90, in _check_for_uri_param
    return get_paramfile(value)
  File "/usr/local/lib/python2.7/dist-packages/awscli/paramfile.py", line 44, in get_paramfile
    data = PrefixMap[prefix](prefix, path)
  File "/usr/local/lib/python2.7/dist-packages/awscli/paramfile.py", line 56, in get_file
    return f.read()
  File "/usr/lib/python2.7/codecs.py", line 296, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf8' codec can't decode byte 0x8b in position 1: invalid start byte
2014-06-16 16:30:30,526 - MainThread - awscli.clidriver - DEBUG - Exiting with rc 255

I'm running with:

$ aws --version
aws-cli/1.3.17 Python/2.7.6 Linux/3.13.0-30-generic

[spazm]

+1 also affected.