Removing .idea from .gitignore

The project cannot include every editor's
ignore files. Contributers can use a local
global gitignore : https://help.github.com/articles/ignoring-files

Signed-off-by: Ankush Agarwal <ankushagarwal11@gmail.com>

.gitignore

@@ -13,7 +13,6 @@
 .git/
 .gopath/
 .hg/
-.idea
 .vagrant*
 Vagrantfile
 a.out