Scott Lamb 0cc4d191c0 bump minimum Rust version to 1.26
1.25 also fails with the upgraded reffers because u128 isn't stable:

error[E0658]: 128-bit type is unstable (see issue #35118)
   --> /home/travis/.cargo/git/checkouts/reffers-rs-0d00fc7f893338b3/49a4d75/src/rc_bitmask.rs:194:34
    |
194 | rc_bit_mask_internal!(primitive, u128, 42, 42, 42);
    |                                  ^^^^
2018-08-27 21:32:51 -07:00
..
2018-08-24 21:04:13 -07:00