bump version to 0.7.0

[marcospb19]

Changed

• No longer give a hard error when a custom toolchain gives an error #67
• Don't print colors when stdout is not a terminal #69
• Add long --verbose and --recursive flags #73
• Make -r/--recursive traverse beyond Cargo directories #78
• Reduce non-verbose output to make it less noisy #81
• Refactor and add -m as a short flag for --maxsize #87
• Only show toolchain list once when using --installed #88
• Support multiple projects as input via CLI #101

Fixed

• When rustc fails, show stderr if stdout is empty #63
• Kibibytes are now printed as KiB, not kiB #69
• Exit with non-zero status on failure #72
• Keep stamp file on dry run #100

[marcospb19]

Postponed while I take a look at #110.