[ci] travis ci build

[bobzhang]

No description provided.

[bobzhang]

the failure is due to the runtime is implemented (assume we have patched the stdlib), to make it universal, we should lift such assumption

[bobzhang]

I learned it a hard way.. the [cmi_format] is different, Marshal will segfault, which means if we want to go cross-compile, we should not rely on the stdlib by the crossed compiler so we have to bump cmi_magic_number first.

Even if we manage to avoid reading any cmi files from stdlib(of the old compiler), the merlin built using ocaml 4.02.3 will not be compatible with bucklescript, seems the cost is pretty high.

Let's put the idea of cross compilng on hold

[coveralls]

Coverage remained the same at 53.446% when pulling 0f76e88 on travis_ci_continue into 90c4290 on master.

[coveralls]

Coverage remained the same at 53.446% when pulling f25ebc4 on travis_ci_continue into 90c4290 on master.