GoToDefinition/Declaration commands for C-family

These are accessible through the :YcmCompleter command. The docs have more
information.
More docs on the new go-to-definition/declaration
Ignoring mappings in our vim 'normal' invocation
Replace YcmCommand with YcmCompleter in README.md
Note about the jumplist mappings in docs
Merge pull request #226 from mmlb/master

README has YcmCommand instead of YcmCompleter
Style fixes for C++
Return an empty location instead of segfaulting
Adding the CONTRIBUTING file
Merge pull request #231 from weslem/master

Prevent segfaults on Goto* with unparseable files
Using event.is_set to be compatible with Python2.6

Fixes #227
Forcing the critical 'B' flag in cpoptions

Fixes #223.
Github now serves page from github.io; update docs
Some rewording for the CONTRIBUTING doc
Fix traceback print on None for |location|

This happens when the user invokes a GoTo* command on a file with no compilation
flags.
Update install.sh

Added more efficient option to detect number of cores on running system via nproc
Merge pull request #240 from izx64/patch-1

Update install.sh
Refactoring the way install.sh checks for commands
Removing some dead code
Refactoring out some vim.eval calls

s:completion_start_column should not be evaled in Python code. That was a
stopgap measure that ended up lasting far longer than intended.