Add a file to test tank links
Use replace task to add create space link at build time

When building twikifier, provide an optional flag to grunt to build the code with a custom create space link function.  This used to be a function hard-coded to tiddlyspace.com

This flag represents the target installation and the default is 'tiddlyspace'

The README will be updated to reflect this when ready.
Add a function to create tank links

This code can be included at build time by running:

    grunt --installation=tank

 This should hopefully address #34 but a review from @cdent would be useful.
Remove host from the link as per @cdent suggestion
Allow createTagButton to be a build configurable function
Update README to reflect custom installation builds
Merge pull request #35 from tiddlyweb/swappable-space-link-function

Swappable createSpaceLink and createTagButton functions at build time