Link to gmock and implement a simple command line builder
Implemented command line construction
Added a new systempaths module for splitting up strings we get from $PATH
Make the tests pass
Bootstrapped the re-execution code and tests, split mocks out into a
new library and added a simple OS abstraction layer
Implemented RelaunchIfNecessary and fixup the tests
Add a quick TODO note
Use the provided argv provided by the command line builder and not
the original program argv
Pass a vector of environment variables to RelaunchIfNecessary
Implemented yiqi::commandline::Environment with accompanying tests.

Also provided a test fixture for checking that value types behave in a
sane manner (ValueTypeConformance). Pulled out the ExceptionCleanup
class into the yiqi::util::ExceptionCleanup namespace.
Switch to using execvpe and provide ycom::Environment
Added constant for __YIQI_INSTRUMENTATION_TOOL_ACTIVE, added a test to
ensure that this env is set
Split out the argv and env determination from RelaunchIfNecessary and start
rewriting that function in terms of those other split out functions
Get the tests passing
Remove empty namespace
Split the ArrayFitsMatchers matcher out into its own library
Deliver the first integration tests, split out shared re-execution data
into a new library
Bootstrapped acceptance tests and get the main part of Yiqi working -
namely, re-execution under some instrumentation tool

Fixes #3