Caching compiled templates

Fixes https://github.com/Financial-Times/o-date/issues/6
Merge pull request #9 from Financial-Times/template-caching

Caching compiled templates
Documented browser support
Merge pull request #10 from Financial-Times/browser-support

Documented browser support
Fixed merge conflicts
Fails gracefully if datetime not defined
typo
Fixed ifs
Fixed merge conflicts
Merge pull request #13 from Financial-Times/datetime-fail

Fails gracefully if datetime not defined
Updated readme to mention that the module should mainly be used to express relative time
Merge pull request #14 from Financial-Times/readme-issue11

Updated readme to mention that the module should mainly be used to expre...
Merge branch 'master' of https://github.com/Financial-Times/o-date into init
Changed createallin and init into just one init function following the specs. Also added back the odomcontentloaded event but it only registers it in a browser environment