Adds testcompress with one basic testcase
Adds compress.hpp

Called as compress(data, selectors), each element in data is 'yielded'
only if the corresponding element in selectors is evaluated as true.
Otherwise it is skipped.  If there are fewer elements in data than
selectors, or vice versa, the loop terminates at the end of the shorter
sequence.
Adds testcompress to Makefile
Adds more tests for compress
Adds testcompress to .gitignore
Merge branch 'master' of https://github.com/ryanhaining/cppitertools

Conflicts:
	tests/.gitignore
	tests/Makefile