Highlight interpolation in heredocs
partially fixed case indentation

- insertion mode still doesn't work correctly
Merge pull request #63 from LnL7/fix-case-indent

partially fixed case indentation
Improve pipeline indentation

Following @josevalim suggestion(https://github.com/elixir-lang/vim-elixir/pull/54#issuecomment-31294774)
for pipeline indentation.

Using:

```elixir
bar
|> baz
|> quux

foo = bar
      |> baz
      |> quux
```
partially fixed case indentation

- insertion mode still doesn't work correctly
Merge pull request #61 from kassio/master

Improve pipeline indentation
Merge pull request #62 from thmzlt/hl-interp-docstr

Highlight string interpolation in heredocs
Fix sigils surrounded with stringDoc("""|''')

Fix #50.

For sigils surrounded with stringDoc skip quotes in sigils content
Link elixirDocString to String instead of Comment
Fix indentation specs

Remove all indentation before force vim to indent to check if vim indent
the code right.
Add the new \\ (default argument) as operator
Merge pull request #67 from LnL7/default-argument

Add the new \\ (default argument)  #65 as operator
Added new sigil syntax

- `~s' and `~S' - Returns a string
Merge pull request #68 from LnL7/new-sigil-syntax

Added new sigil syntax