Add .ensime_cache to gitignore

[mikejcurry]

I just installed and started using ensime in Atom. For cats it created a .ensime_cache directory following the default setup steps, so I guess it makes sense to add this .gitignore for the project.

[adelbertc]

In light of the fixed build (#954) this need to be re-merged against the latest master. Sorry about that!

[codecov-io]

Current coverage is 88.88%

Merging #949 into master will decrease coverage by -0.05% as of c86a2a2

@@            master    #949   diff @@
======================================
  Files          179     180     +1
  Stmts         2133    2142     +9
  Branches        42      42       
  Methods          0       0       
======================================
+ Hit           1897    1904     +7
  Partial          0       0       
- Missed         236     238     +2

Review entire Coverage Diff as of c86a2a2

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[fthomas]

👍

[adelbertc]

👍