Updated the .gitignore to ignore the generated lexer/parser files for FsLex and FsYacc.
Modified project files so they can be built on Mono, and on Windows when the VS2013 build tools are installed alongside VS2012.
Modified the FsLexYacc.Runtime project file so it targes the .NET 4.0 client profile instead of the full profile.
Merge pull request #11 from jack-pappas/project-fixes

Fixes to project files to allow building with VS2012+VS2013 Build Tools (and Mono)