Allow NPROCS to be specified on command line at build time

make NPROCS=1 # to force a parallel build
Merge pull request #120 from Vizzuality/serialbuild

Allow NPROCS to be specified on command line at build time
allow building against Mapnik 2.2.0-pre without warning
fix test name - refs mapnik/mapnik#1454
use mapnik's new geojson plugin instead of ogr to read geojson files
adapt to mapnik 2.2.0-pre code upstream as per https://github.com/mapnik/mapnik/issues/1451
no need for ifdefs, calling instance() should work for older mapnik as well
bump to 0.7.11
Adapt to mapnik 2.2-pre singleton changes
bump to 0.7.12 with more fixes to keep up with Mapnik API
fix compile with <= Mapnik 2.1.0 and bump to 0.7.13
add a catch all symbolizer to avoid compile error when new ones are added (like debug symbolizer)
bump to 0.7.14
mapnik-inspect.js - support rasters as well
thanks to new clang warning (comparison of constant with expression of type 'bool' is always false) fix a few faulty argument checks
bind arg is going away in mapnik soon (mapnik/mapnik#962) so remove it - also closes #124
fix output for mapnik-inspect on shapefiles
bump to 0.7.15
add 0.7.15 changelog entry
fixup argument checkout to avoid msvc 'unsafe use of type' warning - refs mapnik/mapnik#1527