* Install rules and dynamic library loading fixes.

A batch of fixes:

- Added 'install' rule to cmake and make, which installs runtime
  headers and library (libtvm_runtime).

- Added 'installdev' rule to make, which also installs the compiler
  infrastructure headers and library (libtvm)

- Added 'INSTALL_DEV' option to cmake, for toggling installation
  of compiler infrastructure headers and library

- cmake no longer builds into lib/ directory; instead all build
  products go in your build directory

- New algorithm for dynamic library loading, as described in #281.

Signed-off-by: Edward Z. Yang <ezyang@fb.com>

* Emit dylib on OS X

Signed-off-by: Edward Z. Yang <ezyang@fb.com>

* Lint fixes.

Signed-off-by: Edward Z. Yang <ezyang@fb.com>