Fixes #672.  Long ints are not handled correctly in Unit constructors.
added "-q" back in to split out pip installs.

The -q was eliminated previously because travis kills the test if
it spends >=5 min without any output.  But each of the pip calls
seem to be <5 min, just *together* they take >5.
changed "OPTIONAL" to "OPTIONAL_DEPS"
sigma_slip was moved to stats -> change docstring accordingly
Merge pull request #688 from astrofrog/config/fix-config-file-affiliated

Fix generate_default_config to work with affiliated packages
Merge pull request #698 from hamogu/docutypo

sigma_slip was moved to stats -> change docstring accordingly
Merge pull request #672 from mdboom/unit/long_int_handling

Unit conversion on quantities mishandles long values
Merge pull request #699 from eteq/travis-yml-split-optionals

Hide log for dependencies installs in travis
Adds a prereleaser hook for zest.releaser to update the VERSION variable in setup.py. This used to work out of the box but we changed it from 'version' to 'VERSION' and now it no longer works.  I need to submit an upstream fix to zest.releaser to make this case-insensitive. This works in the meantime.
Merge branch 'master' of github.com:astropy/astropy
Started improving Quantity docs