Updated to latest ycmd
Fix handling of signs placed by other plugins

It appears to address numerous amount of issues, including: #812, #801, #887.

Proposed solution uses dummy sign which is placed before updating
diagnostic signs and unplaced afterwards, which eliminates any
flickering. Also, it not just unplace all, it unplaces only that marks
that are changed, so performance should not be an issue in case of many
diagnostic messages.

It's common solution that can be found in some vim plugins that manage
signatures.

Signed-off-by: Stanislav Seletskiy <s.seletskiy@gmail.com>
Minor refactoring & stylistic changes.
Merge branch 'seletskiy-master2'
`set -e` in install.sh

This allows error in `build.sh` to propagate up. Fixes #1197.
Merge pull request #1201 from oconnor663/master

`set -e` in install.sh
Now using a libclang based on Clang 3.5.

This is now the officialy supported version of libclang for YCM. The
changes come as a result of updating to the latest ycmd commit.
Propagate exception stacks though futures.
Crude razor support
Pass extra_data from completion result to vim completion
Add vim function to get previous completions for CompleteDone autoevent