remove universal build flags from makefile

removed -arch i386 from makefile to build specifically on x86_64 to fix:

/sw/include/curl/curlrules.h:143:6: error: '__curl_rule_01__' declared
as an array
with a negative size
[CurlchkszEQ(long, CURL_SIZEOF_LONG)];
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/sw/include/curl/curlrules.h:132:27: note: expanded from macro
'CurlchkszEQ'
#define CurlchkszEQ(t, s) sizeof(t) == s ? 1 : -1
Merge pull request #29 from megrimm/osx-10.9_json-c-0.10

remove universal build flags from makefile