Bump version to 1.0.0.

Commit b37008903a9fb7102325a8cd8efc1cc2643cd76e introduced a breaking
change (renaming Membrane::Schema to Membrane::Schemas), which was
published in version 0.0.4.

Versions 0.0.4 and 0.0.5 will be yanked from RubyGems. If you require
the changes in these versions, please update your Gemfile to require 1.0.0.

Signed-off-by: Tammer Saleh <tammer@pivotallabs.com>