Version bump to 0.19.0.pre
Merged 0.18.4 changes in 0.19.0
Updated to contour 2.0.0
Updated to pg 0.16.0
Updated to redcarpet 3.0.0
Updated to carrierwave 0.9.0
SAS export now properly escapes single quotes ``'`` in labels using two single quotes ``''``, fixes #12.
Numeric variables can now be entered without a leading zero without causing a validation error, fixes #8.
Removed `Clear` button from radio and checkbox groups as it is no longer needed, closes #13.
Replaced btn-danger with less intrusive btn-danger-inverse
Updated the login page
Changelog styling
Updated to rails-observers 0.1.2
README styling
Fixed variable display name not showing up on the design editor when set as scale alignment without a domain, fixes #14.
`Enter` and `Escape` now work as expected on design editor, fixes #15.

Hitting `Enter` while editing design or variable names on the design editor now correctly updates the name

Additionally, hitting `Escape` will close the modal popup
Removed redundant tooltips for integer, numeric, and string variables, closes #17.
Removed redundant tooltips for text variables, closes #17.
SAS export now properly escapes single quotes ``'`` in labels using two single quotes ``''``, for domains too, fixes #12.
Added hexdigest to zip file names to avoid clashing namespaces