Fix undefined variables throwing exception with length filter
fix using `include` and a few other forms within macros (fixes #159)
relax parseTemplateRef and allow any arbitrary expression (fixes #269)
Merge pull request #248 from garygreen/fix/length-undefined

Fix undefined variables throwing exception with length filter
also relax `import` to take an expression
clarify `env.addGlobal` method
prep for 1.0.6
fix versioning in browserfiles, bump to 1.0.7
Merge remote-tracking branch 'origin/master'
rebuild browserfiles