References:
http://en.wikipedia.org/wiki/Library_Exchange_Format
http://www.csee.umbc.edu/~cpatel2/links/641/slides/lect04_LEF.pdf
http://electronics.stackexchange.com/questions/77068/please-explain-tech-lef-tech-lib
http://www.cs.utah.edu/~rfonnesb/ee6961/tutorials/techfile/