Provide more context for the usage of the ARGV
Expanded interface so it will be easier to add parallism.
Moved more logic from the executable script into the library.
Fixed inconsistent formatting.
Added version message and tidied code in main file.
Added thread pool.
Removed unused required.
Changed PdfPageCounter thread pool size configurable.
Added setting the number of threads used by the PdfPageCounter to the binary options.
Merge branch 'feature/threads' into develop

Conflicts:
	lib/pdf-page-count/pdf_page_counter.rb
Added dependencies.
Merge branch 'feature/threads' into develop
Update gem spec with rb files.
Updated release information.
Updated license to match the BSD-3-Clause license published at http://opensource.org/licenses/BSD-3-Clause.
Merge branch 'release/1.0.0'