v0.2.2: Version 0.2.2. More fixes.

Lots of changes.

• Fixed Coveralls, nosetests.
• Changed k-means clustering to use larger values of k in squared steps, e.g. 4, 9, 16, 25.
• k_range argument passed to clustering functions is now k_vals since it now accepts lists of values rather than just start and end values for a range.
• Changed Pandas data frame sort methods from df.sort() to either df.sort_index() or df.sort_values(by='colname').
• Updated README.md.