Merge pull request #1 from abbat/patch-1

* Fix nginx crash on signal 11 when gridfs_find_query returns MONGO_ERROR
NaN workaround for gridfile_get_numchunks (mongo_c_driver/src/gridfs.c).

gridfile_get_numchunks returns -2147483648 when chunkSize is 0
(converting NaN to int). Conversion this int to ngx_uint_t produce
2147483648 and next ngx_pcalloc throws out of memory.
Merge pull request #2 from abbat/master

NaN workaround for gridfile_get_numchunks (mongo_c_driver/src/gridfs.c).
Switching submodule: removed original submodule.
Switching submodule: added new submodule.
Added connection resuming.
Ignoring the connection error during nginx starting up.
fixed submodule url
bug fixed: failed to connect to the replica set nodes which are indicated with the hostname. (In the some environment, the db.isMaster command returns a hostname, not an IP address.)
add range query support (quick hack)
Merge remote-tracking branch 'kiwanami/master'