Switch off scaladoc generation for Scala 2.10 due to macro problems

[mikejcurry]

This PR would switch off scaladoc generation for Scala 2.10 during the makeSite process. The site generated in 2.10 mode would not have scaladoc generated, but would be otherwise identical to the site generated in 2.11 mode.

This allows documentation to be put together for all classes, and should allow #898 to pass the build.

[ceedubs]

Sounds good to me if it should fix #898. Thanks!

[codecov-io]

Current coverage is 89.78%

Merging #958 into master will not affect coverage as of 960a9ed

@@            master    #958   diff @@
======================================
  Files          180     180       
  Stmts         2144    2144       
  Branches        42      42       
  Methods          0       0       
======================================
  Hit           1925    1925       
  Partial          0       0       
  Missed         219     219       

Review entire Coverage Diff as of 960a9ed

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[rossabaker]

I did the same for http4s for the same reason, and haven't had any regrets.