Lifshitz Law Firm, P.C. Announces Investigation of Akcea Therapeutics, Inc. (NASDAQ: AKCA), BMC Stock Holdings, Inc. (NASDAQ: BMCH), Builders FirstSource, Inc. (NASDAQ: BLDR), Cancer Genetics, Inc. (NASDAQ: CGIX), Cellular Biomedicine Group, Inc. (NASDAQ: CBMG), Otelco Inc. (NASDAQ: OTEL), Rosetta Stone Inc. (NYSE: RST), Varian Medical Systems, Inc. (NYSE: VAR), and Yintech Investment Holdings Limited (NASDAQ: YIN)