Merge pull request #235 from munslowa/master

Citation information section
Improved the gridline interface. This is an intermediate step to improving the overall functionality of Cartopy gridlines & is by no means a future-proof API.
change from @article to @manual as recommended

Signed-off-by: Andrew Munslow <munslowa@gmail.com>
Merge pull request #240 from munslowa/citation_update

Change from @article to @manual in citation recommendation.
Fixed PEP8 whitespace problems.
Sped-up repeated documentation building.
Review actions.
Review action.
Fixed tolerance of gridliner_labels test to make travis-ci test to pass.
Added a version switcher on the documentation.
Merge pull request #242 from pelson/doc_build_speedup

Sped-up repeated documentation building.
Changed the shapefile used in the hurricane example so that the great lakes are not included in the states.
Merge pull request #238 from pelson/tickmark_control

Improved the gridline interface.
Updated version switcher to point to scitools domain.
Merge pull request #247 from pelson/hurricane_with_lakes

Exclude great lakes in hurricane example
Commented on the use of the *latest* version switcher, rather than the local one.
Merge pull request #244 from pelson/version_switcher

Added a version switcher on the documentation.
Merge remote branch 'upstream/v0.6.x' into HEAD

* upstream/v0.6.x:
  Commented on the use of the *latest* version switcher, rather than the local one.
  Updated version switcher to point to scitools domain.
  Changed the shapefile used in the hurricane example so that the great lakes are not included in the states.
  Added a version switcher on the documentation.
  Review action.
  Sped-up repeated documentation building.
Preparation for a v0.7.0 release.
Tidied up some of the v0.7 documentation.