Fix memory leak.

[phoemur]

As you know, plain C has not RAII, so the structure created in

tinycurl/tinycurl.cpp

Line 29 in 00b89ff

struct curl_slist *chunk = NULL;

Is never deallocated by the underlying library. I opted in this pull request to let this structure as a private member and clean in the destructor:
https://github.com/phoemur/tinycurl/blob/b95a68f84ecc171638d00b5de688869f9d7493f3/tinycurl.cpp#L24

Also improved the resource creation in the constructor and better cleanup in this pull request.
This small change seems to make a huge difference, as you can see:

Valgrind before changes:
`
==3320==

==3320== HEAP SUMMARY:

==3320==     in use at exit: 96,824 bytes in 3,233 blocks

==3320==   total heap usage: 4,324 allocs, 1,091 frees, 391,637 bytes allocate

==3320==

==3320== LEAK SUMMARY:

==3320==    definitely lost: 0 bytes in 0 blocks

==3320==    indirectly lost: 0 bytes in 0 blocks

==3320==      possibly lost: 0 bytes in 0 blocks

==3320==    still reachable: 96,824 bytes in 3,233 blocks

==3320==         suppressed: 0 bytes in 0 blocks

==3320== Reachable blocks (those to which a pointer was found) are not shown.

==3320== To see them, rerun with: --leak-check=full --show-leak-kinds=all

==3320== 

==3320== For counts of detected and suppressed errors, rerun with: -v

==3320== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

`

Valgrind After changes:
`
==3419==

==3419== HEAP SUMMARY:

==3419==     in use at exit: 528 bytes in 10 blocks

==3419==   total heap usage: 4,324 allocs, 4,314 frees, 391,637 bytes allocated

==3419== 

==3419== LEAK SUMMARY:

==3419==    definitely lost: 0 bytes in 0 blocks

==3419==    indirectly lost: 0 bytes in 0 blocks

==3419==      possibly lost: 0 bytes in 0 blocks

==3419==    still reachable: 528 bytes in 10 blocks

==3419==         suppressed: 0 bytes in 0 blocks

==3419== Reachable blocks (those to which a pointer was found) are not shown.

==3419== To see them, rerun with: --leak-check=full --show-leak-kinds=all

==3419== 

==3419== For counts of detected and suppressed errors, rerun with: -v

==3419== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)`

I could not eliminate all leaks, though going from 96,824 to 528 bytes in use at exit semmed worth a pull request.

Thanks for your attention

[phoemur]

Also noted that the remaining bytes left behind here allocated by curl itself through libcrypto:
CRYPTO_malloc (in /lib64/libcrypto.so.1.0.0)

So there's not much we can do about it.

[asashnov]

I'm not sure this will work with C++ 98

[phoemur]

I have no C++98 compiler at hand, but since this is libcurl interface,which is plain old C, maybe its worth a try...