Revert #include ordering in SmilesMolSupplier.cpp
Revert #include ordering in SmilesMolSupplier.cpp

Recent commit 3358ec592580bae8a22faee90336f396db69de01 swapped around `#include <string>` and `include <boost/python.hpp>` in SmilesMolSupplier.cpp.

This caused compilation to fail on Mac OS X with errors related to `toupper`, `tolower`, `isupper`, etc. macros being redefined in pyport.h within the Python installation. From a Google search, I believe it is related to this problem:  http://bugs.python.org/issue10910

This commit simply swaps back `#include <string>` to come after `include <boost/python.hpp>`, which appears to solve the problem.

AlexanderSavelyev/rdkit,greglandrum/rdkit,soerendip42/rdkit,strets123/rdkit,rvianello/rdkit,soerendip42/rdkit,rvianello/rdkit,rdkit/rdkit,greglandrum/rdkit,adalke/rdkit,rdkit/rdkit,soerendip42/rdkit,rvianello/rdkit,adalke/rdkit,rvianello/rdkit,jandom/rdkit,ptosco/rdkit,greglandrum/rdkit,ptosco/rdkit,AlexanderSavelyev/rdkit,AlexanderSavelyev/rdkit,AlexanderSavelyev/rdkit,bp-kelley/rdkit,bp-kelley/rdkit,strets123/rdkit,greglandrum/rdkit,adalke/rdkit,strets123/rdkit,AlexanderSavelyev/rdkit,strets123/rdkit,adalke/rdkit,rdkit/rdkit,soerendip42/rdkit,rdkit/rdkit,greglandrum/rdkit,soerendip42/rdkit,bp-kelley/rdkit,ptosco/rdkit,ptosco/rdkit,strets123/rdkit,bp-kelley/rdkit,AlexanderSavelyev/rdkit,jandom/rdkit,jandom/rdkit,AlexanderSavelyev/rdkit,adalke/rdkit,bp-kelley/rdkit,soerendip42/rdkit,jandom/rdkit,ptosco/rdkit,rdkit/rdkit,jandom/rdkit,ptosco/rdkit,rvianello/rdkit,adalke/rdkit,greglandrum/rdkit,ptosco/rdkit,strets123/rdkit,rdkit/rdkit,greglandrum/rdkit,soerendip42/rdkit,ptosco/rdkit,rvianello/rdkit,adalke/rdkit,jandom/rdkit,jandom/rdkit,jandom/rdkit,greglandrum/rdkit,bp-kelley/rdkit,rdkit/rdkit,bp-kelley/rdkit,AlexanderSavelyev/rdkit,AlexanderSavelyev/rdkit,strets123/rdkit,rdkit/rdkit,adalke/rdkit,rvianello/rdkit,bp-kelley/rdkit,soerendip42/rdkit,strets123/rdkit,rvianello/rdkit