As part of #330 I made a pass on ensuring that the proj4 string representing mercator was consistent across apps, to ensure that phony and expensive reproduction would never happen in TileMill/Mapnik.
It appears we still have some inconsistency around +y_0=0.0 vs +y_0=0 after 7d8497f.
fix canonical representation of mercator to match tilemill - refs map…
fix handling of +y_0=0.0 vs +y_0=0 - refs mapbox/tilemill#1866
keep proj4 strings on one line to make it dead easy to grep - refs #1866
fix proj4 strings in example projects - refs #1866