Allow backup to space separated files in interval parsing

Issue #27 resolved
Brad Chapman
created an issue

Based on a discussion at BioStar:

It was suggested that interval parsing should also handle "tab" separated files that are actually separated by spaces. This patch adds a allow_spaces=True argument that will try space separating a line if it fails by tab separation:

reader = GenomicIntervalReader(file, allow_spaces=True)

It could be configurable for other whitespace separators as well if other cases come up. See the suite of bed test files at: