Update BSON_README.md

Completed unfinished statement about which settings turn off reading and writing of splits information
Added Lazy BSON as a format type
Merge pull request #70 from solarmicrobe/patch-1

Update BSON_README.md
Verify that there is a valid output URI set before trying to write any records HADOOP-81
Merge pull request #72 from sweetieSong/issue/add-lazybson-input

Added Lazy BSON as a input type
move environment-specific settings to the top of script, set in bash vars
Merge branch 'master' of https://github.com/mongodb/mongo-hadoop
round-robin target shards by re-ordering splits/chunks for sharded collections.