Merge pull request #158 from c42f/cjf-warnings-fix

Fix various compiler warnings and minor bugs
increment boost to 1.54, add asio, string_ref, and regex
update script for bcp'ing 1.54
compile new additions for 1.54
Merge pull request #160 from PDAL/issues/160-upgrade-boost-154

Upgrade boost to 1.54
Merge remote-tracking branch 'upstream/master' into getDimension_optimization
getDimension perf tests + use string_ref for dimension names

* Convert C-style implementation of getDimensionPtr() to use
  boost::string_ref for clarity.

* Add performance test cases to exercise various usages of
  Schema::getDimension*().  These underscore the importance of avoiding
  exceptions here, which are roughly 100x as expensive as a dimension
  lookup.

* Included with performance tests is a helpful header from OpenImageIO
  for convenient high resoultion timing.