Fix clang warnings

These changes fix several clang warnings when building on OS X.

* Ignore build artifacts from source control
* Fix several "warning: no newline at end of file [-Wnewline-eof]"
* Fix the following warnings:

```
src/haywire/http_request.c:32:9: warning: implicit declaration of function 'free' is invalid in C99 [-Wimplicit-function-declaration]
        free(context->request->url);
        ^

src/haywire/http_request.c:38:40: warning: implicitly declaring library function 'malloc' with type 'void *(unsigned long)'
    context->request = (http_request *)malloc(sizeof(http_request));
                                       ^
src/haywire/http_request.c:38:40: note: please include the header <stdlib.h> or explicitly provide a declaration for 'malloc'

src/haywire/http_server.c:16:39: warning: extra tokens at end of #include directive [-Wextra-tokens]
                                      ^
                                      //
src/haywire/http_server.c:35:9: warning: unused variable 'i' [-Wunused-variable]
    int i;
        ^

src/haywire/http_server.c:36:11: warning: unused variable 'value' [-Wunused-variable]
    char *value;
          ^

src/haywire/http_server.c:109:20: warning: comparison of integers of different signs: 'size_t' (aka 'unsigned long') and 'ssize_t' (aka 'long')
      [-Wsign-compare]
        if (parsed < nread)
            ~~~~~~ ^ ~~~~~

src/haywire/http_server.c:145:18: warning: unused variable 'parser' [-Wunused-variable]
    http_parser *parser = (http_parser *)req->data;

src/haywire/http_server.c:146:27: warning: unused variable 'context' [-Wunused-variable]
    http_request_context *context = (http_request_context *)parser->data;
                          ^

src/haywire/trie/radix.c:57:32: warning: comparison of integers of different signs: 'int' and 'unsigned long' [-Wsign-compare]
    while (*k1 == *k2 && count >= sizeof(int) * 8) {
                         ~~~~~ ^  ~~~~~~~~~~~~~~~
```