CORE-210 pyiso8583 support (#112)

* CORE-210 iso8583 test

* Iso parser running

* removed odd imports from iso test

* decode test working

* a minor change

* reverted an accident

* mutalibility from thread

* pyiso8583 test parser

* a minor

* renamed ISO decoder

* tests renamed

* set union

* no 2 field

* fixed by mahmoudimus

* encode first attempt

* fields encoding working

* fixed bitmap processing

* bitmap fix

* a minor

* encode/decode with test_payload test fix

* test renaming

* enc_field_len_str fix

* test encoder bitmaps

* spec star

* added two tests of encoder

* removed jpos support (

* an import fix

* unhexlify

* deleted odd file

* no header in spec test

* test_non_string_field_keys