bit packing support for LE
Merge pull request #57 from Parquet/bit_packing_lsb_first

bit packing support for LE
Address first round of comments
Merge branch 'master' into alexlevenson/RLE-bit-packing-hybrid

Conflicts:
	parquet-column/src/main/java/parquet/column/Encoding.java
	parquet-column/src/main/java/parquet/column/values/rle/RLESimpleEncoder.java
	parquet-column/src/main/java/parquet/column/values/rle/RunLengthBitPackingHybridDecoder.java