Explain how to generate cmake flags db.

Relevant to Valloric/YouCompleteMe#1084
Add Go support for tag file reading.

Fixes Valloric/YouCompleteMe#1094.
Resolving IndexError issues with unicode in buffer

When the user is typing on a line that has non-ASCII chars,
CompletionStartColumn tends to screw things up because it used to assume every
byte is a char, which isn't true.

Fixes #788.
Clarify that line/column numbers are byte offsets.
Minor rewording in README
example_client sends goto requests

Also requests for defined subcommands.
Minor extra comments for example_client
More docs on ycmd behavior
Relicensing example code under Apache2
README rewording.
More docs on ycmd internals
Fix warning on CMake 3.0
Docs on how to build ycmd
Fix build instructions command line
Minor tweak to Building command line

So that it's easy to copy/paste.
More info on building ycmd
Examples README mentions ycmd needs to be built
Add support for WantImportableTypes in C# completer
Add tests for WantImportableTypes in C# completer
Update travis config to install mono 3