Bulk API fixes

o We didn't manage the index offsetting correctly for bulk inserts.
o We didn't massage errors into writeErrors for legacy operations
cluster: explicitely check for NULL replSet.

Fixes CDRIVER-409.
Merge pull request #65 from hanumantmk/writeErrorFix

Bulk API fixes
allow bulk op insert for w:0 bulk inserts

o fixes a performance regression for 2.6 w:0 writes
o allows w:0 writes to fast path out of the bulk api on 2.4
Add a link to the docs
Merge pull request #67 from bjori/patch-3

Add a link to the docs
CDRIVER411 never send a negative nToReturn

Remove logic that sends nToReturn to avoid missing documents that don't
fit in the initial batch.
finally get the correct nToReturn value

if command:
    1

if batch size:
    if limit:
        min(batch_size, limit)
    else:
        batch_size

0
client: apply read preference tags from mongoc_uri_t.
cluster: set proper error if we fail to locate a node.

This could happen if read preferences prevent finding a suitable node.
build: add $(BSON_LIBS) for mongoc-rpc-validate test program.

This should fix builds on systems like Ubuntu with non-standard GNU ld
configurations.
build: fix build on centos 6.5
git: update .gitignore to ignore *.gz
build: bump libbson
Merge branch 'mongodb-master'

Conflicts:
	src/libbson