PWMEnrich package

Version 2.0.0:
    o General cleanup of the code with various small optimisations
    o A FASTA file name is now also taken as input to motifEnrichment()
    o The output of motifEnrichment() is now wrapped into a class MotifEnrichmentResults
      that provides a number of convenience methods for common tasks like ranking and
      plotting motifs
    o Functions makeBackground() and getBackgroundFrequencies() can now take BSgenome 
      objects as input. Thanks to Diego Diez for suggesting this and providing the code. 
    o Another version of motifScores() has been implemented that requires large amounts
      of memory, but is at least 2 times faster than the old motifScores() implementation.
      Use a new option useBigMemoryPWMEnrich() to switch to this implementation.   
    o PFMtoPWM now accepts a new parameter seq.count so that MotifDb motifs that are 
      expressed as probabilities instead of frequencies can be easily used.  
    
Version 1.3.0:
	o Bioconductor 2.11 release version    

Version 1.0.2:
	o Use core package parallel instead of doMC

Version 1.0.1:
	o Fix a typo in test cases and remove doMC as build dependency

Version 1.0.0:
	o Initial release of the package