Add a warning for integers that are out of range, and truncate their values.
Make to_header_string work (and add a test)
Merge pull request #825 from mdboom/vo/integer-overflow

VOTable: Add a warning for integers that are out of range
Fix to_fits and add a test
Merge pull request #822 from mdboom/wcs/to_header_string_fix

WCS object from default constructor results in strange errors
Merge remote-tracking branch 'kbarbary/effhist' into staging
added matplotlib to travis sphinx build

specific version selected because py 3.x build errors occur on released
version